diff --git a/src/application/index.ts b/src/application/index.ts
index 3061ddb..0506c2f 100644
--- a/src/application/index.ts
+++ b/src/application/index.ts
@@ -20,13 +20,14 @@ import { SimulationScheduler } from '../simulation/scheduler.js';
 import { SignalNormalizer } from '../signals/index.js';
 import { IWalletWatcher } from '../domain/interfaces.js';
 import { RawWalletTransaction } from '../domain/models.js';
-import { fetchTransactionWithRetry } from '../solana/fetcher.js';
+import { BoundedTransactionQueue, BackpressureDropError } from '../solana/fetcher.js';
 
 export class Application {
   public isShuttingDown = false;
   public simulationIntervalId: NodeJS.Timeout | null = null;
   public watcher: IWalletWatcher | null = null;
   public metricsProvider: InfluxMetricsProvider | MockMetricsProvider | null = null;
+  public transactionQueue: BoundedTransactionQueue | null = null;
 
   async bootstrap(): Promise<void> {
     const config = loadConfig();
@@ -131,6 +132,14 @@ export class Application {
         config.SOLANA_RPC_ENDPOINT,
         config.SOLANA_WSS_ENDPOINT,
       );
+      this.transactionQueue = new BoundedTransactionQueue(
+        (this.watcher as any).connection || new (await import('@solana/web3.js')).Connection(config.SOLANA_RPC_ENDPOINT),
+        config.SOLANA_QUEUE_MAX_CONCURRENCY,
+        config.SOLANA_QUEUE_MIN_DELAY_MS,
+        config.SOLANA_QUEUE_MAX_SIZE,
+        this.metricsProvider || undefined,
+      );
+      this.transactionQueue.start();
     } else {
       this.watcher = new MockWalletWatcher(watchedAddresses);
     }
@@ -141,6 +150,14 @@ export class Application {
       const detectedAt = observation.timestamp || new Date();
 
       if (config.WALLET_WATCHER_MODE === 'real') {
+        // Pre-filtering failed transactions:
+        // WebSocket subscriptions (like logs) may provide an "err" field. If err is present, filter it!
+        const wsPayload = (observation as any).rawPayload || {};
+        if (wsPayload.err) {
+          logger.info(`[RealMode] Pre-filtered failed transaction signature ${observation.signature} (logs.err is not null).`, { correlationId });
+          return;
+        }
+
         logger.info(
           `[RealMode] Activity detected for wallet ${observation.walletAddress}. Signature: ${observation.signature}, Slot: ${observation.slot}`,
           { correlationId },
@@ -169,72 +186,110 @@ export class Application {
           observation.walletAddress,
         );
 
-        // Fetch transaction
-        const fetchStartTime = Date.now();
-        await journalService.log(correlationId, 'raw_transaction_fetch_started', {
-          signature: observation.signature,
-        });
-
-        let txPayload: any;
-        try {
-          const connection = (this.watcher as any).connection;
-          if (!connection) {
-            throw new Error('Connection not initialized on RealWalletWatcher');
-          }
-          txPayload = await fetchTransactionWithRetry(connection, observation.signature);
-        } catch (error) {
-          logger.error(`[RealMode] Failed to fetch transaction ${observation.signature}`, error);
-          await journalService.log(correlationId, 'raw_transaction_fetch_failed', {
-            signature: observation.signature,
-            error: error instanceof Error ? error.message : String(error),
-          });
+        // Push item onto the bounded queue for non-blocking execution
+        if (!this.transactionQueue) {
+          logger.error('[RealMode] Transaction queue not initialized!');
           return;
         }
 
-        const fetchEndTime = Date.now();
-        const fetchDuration = fetchEndTime - fetchStartTime;
-        this.metricsProvider?.recordQuoteLatency(fetchDuration, 'rpc_fetch');
-
-        await journalService.log(correlationId, 'raw_transaction_fetched', {
+        const queued = this.transactionQueue.push({
           signature: observation.signature,
-          slot: txPayload.slot,
-          blockTime: txPayload.blockTime,
+          walletAddress: observation.walletAddress,
+          slot: observation.slot,
+          detectedAt,
+          correlationId,
+          onSuccess: async (txPayload) => {
+            await journalService.log(correlationId, 'raw_transaction_fetched', {
+              signature: observation.signature,
+              slot: txPayload.slot,
+              blockTime: txPayload.blockTime,
+            });
+
+            // Calculate balance changes to assess transaction relevance
+            const { isTransactionRelevant } = await import('../solana/parser.js');
+            const relevant = isTransactionRelevant(txPayload, observation.walletAddress);
+
+            this.metricsProvider?.recordTransactionRelevance(relevant);
+
+            if (!relevant) {
+              logger.info(`[RealMode] Classification: IRRELEVANT transaction ${observation.signature} for wallet ${observation.walletAddress}. Excluding from persistence.`, { correlationId });
+              await journalService.log(correlationId, 'transaction_classified_irrelevant', {
+                signature: observation.signature,
+                walletAddress: observation.walletAddress,
+              });
+
+              // If configured to skip storing irrelevant transactions, stop here!
+              if (!config.STORE_IRRELEVANT_RAW_TRANSACTIONS) {
+                return;
+              }
+            } else {
+              logger.info(`[RealMode] Classification: RELEVANT transaction ${observation.signature} detected.`, { correlationId });
+              await journalService.log(correlationId, 'transaction_classified_relevant', {
+                signature: observation.signature,
+                walletAddress: observation.walletAddress,
+              });
+            }
+
+            // Persist raw transaction
+            try {
+              const blockTime = txPayload.blockTime ? new Date(txPayload.blockTime * 1000) : null;
+              
+              if (blockTime) {
+                this.metricsProvider?.recordWalletDetectionLatency(
+                  Date.now() - blockTime.getTime(),
+                  observation.walletAddress,
+                );
+              }
+
+              const rawTx: RawWalletTransaction = {
+                transactionSignature: observation.signature,
+                sourceWallet: observation.walletAddress,
+                slot: observation.slot,
+                blockTime,
+                detectedAt,
+                rawPayload: txPayload,
+                parserVersion: 'ingestion_v1',
+              };
+
+              await rawTxRepo.saveTransaction(rawTx);
+
+              await journalService.log(correlationId, 'raw_transaction_persisted', {
+                signature: observation.signature,
+                slot: observation.slot,
+              });
+
+              logger.info(`[RealMode] Raw transaction ${observation.signature} successfully persisted and pipeline STOPPED.`, { correlationId });
+            } catch (error) {
+              logger.error(`[RealMode] Failed to persist raw transaction ${observation.signature}`, error);
+            }
+          },
+          onFailure: async (error) => {
+            const isBackpressure = error instanceof BackpressureDropError || error.name === 'BackpressureDropError';
+            if (isBackpressure) {
+              const bpError = error as BackpressureDropError;
+              logger.warn(`[RealMode] Transaction dropped due to backpressure: signature ${bpError.signature} for wallet ${bpError.walletAddress}. Depth: ${bpError.queueDepth}, Age: ${bpError.ageMs}ms`);
+              await journalService.log(correlationId, 'transaction_dropped_backpressure', {
+                signature: bpError.signature,
+                walletAddress: bpError.walletAddress,
+                queueDepth: bpError.queueDepth,
+                ageMs: bpError.ageMs,
+              });
+            } else {
+              logger.error(`[RealMode] Failed to fetch transaction ${observation.signature}`, error);
+              await journalService.log(correlationId, 'raw_transaction_fetch_failed', {
+                signature: observation.signature,
+                error: error.message,
+              });
+            }
+          },
         });
 
-        // Persist raw transaction
-        try {
-          const blockTime = txPayload.blockTime ? new Date(txPayload.blockTime * 1000) : null;
-          
-          if (blockTime) {
-            this.metricsProvider?.recordWalletDetectionLatency(
-              Date.now() - blockTime.getTime(),
-              observation.walletAddress,
-            );
-          }
-
-          const rawTx: RawWalletTransaction = {
-            transactionSignature: observation.signature,
-            sourceWallet: observation.walletAddress,
-            slot: observation.slot,
-            blockTime,
-            detectedAt,
-            rawPayload: txPayload,
-            parserVersion: 'ingestion_v1',
-          };
-
-          await rawTxRepo.saveTransaction(rawTx);
-
-          const totalDuration = Date.now() - detectedAt.getTime();
-          this.metricsProvider?.recordSignalProcessingLatency(totalDuration);
-
-          await journalService.log(correlationId, 'raw_transaction_persisted', {
+        if (!queued) {
+          logger.warn(`[RealMode] Signature ${observation.signature} was dropped due to queue backpressure.`, { correlationId });
+          await journalService.log(correlationId, 'raw_transaction_fetch_failed', {
             signature: observation.signature,
-            slot: observation.slot,
+            error: 'Queue backpressure: item dropped',
           });
-
-          logger.info(`[RealMode] Raw transaction ${observation.signature} successfully persisted and pipeline STOPPED.`, { correlationId });
-        } catch (error) {
-          logger.error(`[RealMode] Failed to persist raw transaction ${observation.signature}`, error);
         }
 
         // STOP (No strategy evaluation, scheduler or copy signal creation in real mode!)
@@ -310,14 +365,16 @@ export class Application {
     // 7. Start on-chain watcher
     await this.watcher.startWatching();
 
-    // 8. Run simulator poller non-blockingly every 500ms
-    this.simulationIntervalId = setInterval(async () => {
-      try {
-        await simulationScheduler.processPending(new Date());
-      } catch (err) {
-        logger.error('Error in simulation engine processing loop', err);
-      }
-    }, 500);
+    // 8. Run simulator poller non-blockingly every 500ms (only if NOT in real mode)
+    if (config.WALLET_WATCHER_MODE !== 'real') {
+      this.simulationIntervalId = setInterval(async () => {
+        try {
+          await simulationScheduler.processPending(new Date());
+        } catch (err) {
+          logger.error('Error in simulation engine processing loop', err);
+        }
+      }, 500);
+    }
 
     logger.info('Bot system components started and fully operational.');
   }
@@ -333,6 +390,11 @@ export class Application {
       this.simulationIntervalId = null;
     }
 
+    if (this.transactionQueue) {
+      this.transactionQueue.stop();
+      this.transactionQueue = null;
+    }
+
     if (this.watcher) {
       await this.watcher.stopWatching();
     }
diff --git a/src/config/index.ts b/src/config/index.ts
index ef586e2..fd8ece5 100644
--- a/src/config/index.ts
+++ b/src/config/index.ts
@@ -40,6 +40,22 @@ const configSchema = z.object({
     .transform((val) => (typeof val === 'number' ? val : parseFloat(val)))
     .default(0.05),
   WALLET_WATCHER_MODE: z.enum(['real', 'mock']).default('real'),
+  SOLANA_QUEUE_MAX_CONCURRENCY: z
+    .union([z.string(), z.number()])
+    .transform((val) => (typeof val === 'number' ? val : parseInt(val, 10)))
+    .default(2),
+  SOLANA_QUEUE_MIN_DELAY_MS: z
+    .union([z.string(), z.number()])
+    .transform((val) => (typeof val === 'number' ? val : parseInt(val, 10)))
+    .default(500),
+  SOLANA_QUEUE_MAX_SIZE: z
+    .union([z.string(), z.number()])
+    .transform((val) => (typeof val === 'number' ? val : parseInt(val, 10)))
+    .default(100),
+  STORE_IRRELEVANT_RAW_TRANSACTIONS: z
+    .union([z.string(), z.boolean()])
+    .transform((val) => (typeof val === 'boolean' ? val : val === 'true'))
+    .default(false),
   CONFIGURATION_HASH: z.string().default(''),
 });
 
diff --git a/src/domain/interfaces.ts b/src/domain/interfaces.ts
index 3c4fe8e..fb9edf3 100644
--- a/src/domain/interfaces.ts
+++ b/src/domain/interfaces.ts
@@ -130,4 +130,17 @@ export interface IMetricsProvider {
   recordPortfolioBalance(balanceSol: number, scenario: number): void;
   recordTradePnl(pnlSol: number, scenario: number, tokenMint: string): void;
   recordExcursion(mfeSol: number, maeSol: number, scenario: number, tokenMint: string): void;
+  // Queue & rate limiting metrics
+  recordQueueDepth(depth: number): void;
+  recordQueueRetries(retries: number, signature: string): void;
+  recordQueue429s(signature: string): void;
+  // Extended high-performance queue & relevance metrics
+  recordWalletEventReceived(wallet: string): void;
+  recordWalletQueueDepth(wallet: string, depth: number): void;
+  recordOldestQueuedAge(wallet: string, ageMs: number): void;
+  recordDroppedOldestCount(wallet: string): void;
+  recordTransactionRelevance(relevant: boolean): void;
+  recordRpcRequestRate(requestsPerSecond: number): void;
+  recordQueueProcessed(wallet: string): void;
+  recordRpcFetchError(wallet: string): void;
 }
diff --git a/src/metrics/index.ts b/src/metrics/index.ts
index 7121286..9f073dd 100644
--- a/src/metrics/index.ts
+++ b/src/metrics/index.ts
@@ -91,6 +91,61 @@ export class InfluxMetricsProvider implements IMetricsProvider {
     this.writePoint(p);
   }
 
+  recordQueueDepth(depth: number): void {
+    const p = new Point('queue_depth').intField('depth', depth);
+    this.writePoint(p);
+  }
+
+  recordQueueRetries(retries: number, signature: string): void {
+    const p = new Point('queue_retries').tag('signature', signature).intField('retries', retries);
+    this.writePoint(p);
+  }
+
+  recordQueue429s(signature: string): void {
+    const p = new Point('queue_429s').tag('signature', signature).intField('count', 1);
+    this.writePoint(p);
+  }
+
+  recordWalletEventReceived(wallet: string): void {
+    const p = new Point('wallet_event_received').tag('wallet', wallet).intField('count', 1);
+    this.writePoint(p);
+  }
+
+  recordWalletQueueDepth(wallet: string, depth: number): void {
+    const p = new Point('wallet_queue_depth').tag('wallet', wallet).intField('depth', depth);
+    this.writePoint(p);
+  }
+
+  recordOldestQueuedAge(wallet: string, ageMs: number): void {
+    const p = new Point('oldest_queued_age').tag('wallet', wallet).floatField('age_ms', ageMs);
+    this.writePoint(p);
+  }
+
+  recordDroppedOldestCount(wallet: string): void {
+    const p = new Point('dropped_oldest_count').tag('wallet', wallet).intField('count', 1);
+    this.writePoint(p);
+  }
+
+  recordTransactionRelevance(relevant: boolean): void {
+    const p = new Point('transaction_relevance').tag('relevant', String(relevant)).intField('count', 1);
+    this.writePoint(p);
+  }
+
+  recordRpcRequestRate(requestsPerSecond: number): void {
+    const p = new Point('rpc_request_rate').floatField('req_per_sec', requestsPerSecond);
+    this.writePoint(p);
+  }
+
+  recordQueueProcessed(wallet: string): void {
+    const p = new Point('queue_processed').tag('wallet', wallet).intField('count', 1);
+    this.writePoint(p);
+  }
+
+  recordRpcFetchError(wallet: string): void {
+    const p = new Point('rpc_fetch_error').tag('wallet', wallet).intField('count', 1);
+    this.writePoint(p);
+  }
+
   async close(): Promise<void> {
     if (this.writeApi) {
       logger.info('Closing InfluxDB metrics writer...');
@@ -114,4 +169,15 @@ export class MockMetricsProvider implements IMetricsProvider {
   recordPortfolioBalance(_balanceSol: number, _scenario: number): void {}
   recordTradePnl(_pnlSol: number, _scenario: number, _tokenMint: string): void {}
   recordExcursion(_mfeSol: number, _maeSol: number, _scenario: number, _tokenMint: string): void {}
+  recordQueueDepth(_depth: number): void {}
+  recordQueueRetries(_retries: number, _signature: string): void {}
+  recordQueue429s(_signature: string): void {}
+  recordWalletEventReceived(_wallet: string): void {}
+  recordWalletQueueDepth(_wallet: string, _depth: number): void {}
+  recordOldestQueuedAge(_wallet: string, _ageMs: number): void {}
+  recordDroppedOldestCount(_wallet: string): void {}
+  recordTransactionRelevance(_relevant: boolean): void {}
+  recordRpcRequestRate(_requestsPerSecond: number): void {}
+  recordQueueProcessed(_wallet: string): void {}
+  recordRpcFetchError(_wallet: string): void {}
 }
diff --git a/src/solana/fetcher.ts b/src/solana/fetcher.ts
index 27b09af..274fde8 100644
--- a/src/solana/fetcher.ts
+++ b/src/solana/fetcher.ts
@@ -1,12 +1,14 @@
 import { Connection, VersionedTransactionResponse } from '@solana/web3.js';
 import { logger } from '../logging/index.js';
+import { IMetricsProvider } from '../domain/interfaces.js';
 
 export async function fetchTransactionWithRetry(
   connection: Connection,
   signature: string,
   maxRetries = 5,
   initialDelayMs = 500,
-  maxDelayMs = 4000,
+  maxDelayMs = 8000,
+  metricsProvider?: IMetricsProvider,
 ): Promise<VersionedTransactionResponse> {
   let attempt = 0;
   let delay = initialDelayMs;
@@ -24,8 +26,27 @@ export async function fetchTransactionWithRetry(
       }
 
       logger.warn(`[TransactionFetcher] Transaction ${signature} not found on attempt ${attempt + 1}. Retrying...`);
-    } catch (err) {
-      logger.error(`[TransactionFetcher] Error fetching transaction ${signature} on attempt ${attempt + 1}`, err);
+    } catch (err: any) {
+      const isRateLimit = err && (err.status === 429 || String(err.message).includes('429') || String(err).includes('429'));
+      if (isRateLimit) {
+        logger.error(`[TransactionFetcher] HTTP 429 Rate Limit encountered for ${signature} on attempt ${attempt + 1}`);
+        if (metricsProvider) {
+          metricsProvider.recordQueue429s(signature);
+        }
+        // Use exponential backoff with jitter for HTTP 429
+        const jitter = Math.random() * 200;
+        const rateLimitDelay = Math.min(delay * 3 + jitter, maxDelayMs * 2);
+        logger.warn(`[TransactionFetcher] Rate limit delay: waiting ${rateLimitDelay.toFixed(0)}ms before retry`);
+        await new Promise((resolve) => setTimeout(resolve, rateLimitDelay));
+        attempt++;
+        if (metricsProvider) {
+          metricsProvider.recordQueueRetries(attempt, signature);
+        }
+        delay = Math.min(delay * 2, maxDelayMs);
+        continue;
+      } else {
+        logger.error(`[TransactionFetcher] Error fetching transaction ${signature} on attempt ${attempt + 1}`, err);
+      }
     }
 
     attempt++;
@@ -33,6 +54,10 @@ export async function fetchTransactionWithRetry(
       break;
     }
 
+    if (metricsProvider) {
+      metricsProvider.recordQueueRetries(attempt, signature);
+    }
+
     logger.debug(`[TransactionFetcher] Waiting ${delay}ms before next retry for ${signature}...`);
     await new Promise((resolve) => setTimeout(resolve, delay));
     delay = Math.min(delay * 2, maxDelayMs);
@@ -40,3 +65,245 @@ export async function fetchTransactionWithRetry(
 
   throw new Error(`Transaction ${signature} could not be fetched after ${maxRetries} attempts.`);
 }
+
+export interface QueueItem {
+  signature: string;
+  walletAddress: string;
+  slot: number;
+  detectedAt: Date;
+  correlationId: string;
+  onSuccess: (tx: VersionedTransactionResponse) => Promise<void>;
+  onFailure: (error: Error) => Promise<void>;
+}
+
+export class BackpressureDropError extends Error {
+  public walletAddress: string;
+  public signature: string;
+  public queueDepth: number;
+  public ageMs: number;
+
+  constructor(message: string, walletAddress: string, signature: string, queueDepth: number, ageMs: number) {
+    super(message);
+    this.name = 'BackpressureDropError';
+    this.walletAddress = walletAddress;
+    this.signature = signature;
+    this.queueDepth = queueDepth;
+    this.ageMs = ageMs;
+    this.stack = undefined;
+  }
+}
+
+export class BoundedTransactionQueue {
+  private walletQueues = new Map<string, QueueItem[]>();
+  private walletOrder: string[] = []; // for round-robin scheduling
+  private activeCount = 0;
+  private running = false;
+  private lastRequestTime = 0;
+  private requestCountLastSecond = 0;
+  private rateSecondTimer: NodeJS.Timeout | null = null;
+  private rateLimitTimeout: NodeJS.Timeout | null = null;
+
+  constructor(
+    private connection: Connection,
+    private maxConcurrency: number,
+    private minDelayMs: number,
+    private maxQueueSize: number, // Bounded limit PER wallet queue
+    private metricsProvider?: IMetricsProvider,
+  ) {}
+
+  public start(): void {
+    if (this.running) return;
+    this.running = true;
+    logger.info(`[BoundedTransactionQueue] Started. Concurrency: ${this.maxConcurrency}, MinDelay: ${this.minDelayMs}ms, MaxQueueSize (Per-Wallet): ${this.maxQueueSize}`);
+
+    this.rateSecondTimer = setInterval(() => {
+      if (this.metricsProvider) {
+        this.metricsProvider.recordRpcRequestRate(this.requestCountLastSecond);
+      }
+      this.requestCountLastSecond = 0;
+    }, 1000);
+  }
+
+  public stop(): void {
+    this.running = false;
+    if (this.rateSecondTimer) {
+      clearInterval(this.rateSecondTimer);
+      this.rateSecondTimer = null;
+    }
+    if (this.rateLimitTimeout) {
+      clearTimeout(this.rateLimitTimeout);
+      this.rateLimitTimeout = null;
+    }
+    logger.info('[BoundedTransactionQueue] Stopped accepting new items. Clearing all per-wallet queues.');
+    this.walletQueues.clear();
+    this.walletOrder = [];
+  }
+
+  public getDepth(walletAddress?: string): number {
+    if (walletAddress) {
+      return this.walletQueues.get(walletAddress)?.length || 0;
+    }
+    let total = 0;
+    for (const q of this.walletQueues.values()) {
+      total += q.length;
+    }
+    return total;
+  }
+
+  public getActiveCount(): number {
+    return this.activeCount;
+  }
+
+  public push(item: QueueItem): boolean {
+    if (!this.running) {
+      logger.warn(`[BoundedTransactionQueue] Rejected signature ${item.signature} because queue is not running`);
+      item.onFailure(new Error('Queue is not running')).catch(() => {});
+      return false;
+    }
+
+    if (this.metricsProvider) {
+      this.metricsProvider.recordWalletEventReceived(item.walletAddress);
+    }
+
+    let wQueue = this.walletQueues.get(item.walletAddress);
+    if (!wQueue) {
+      wQueue = [];
+      this.walletQueues.set(item.walletAddress, wQueue);
+    }
+
+    // Check bounded size backpressure per-wallet queue
+    if (wQueue.length >= this.maxQueueSize) {
+      // BACKPRESSURE policy: favor recent transactions!
+      // Drop the OLDEST queued item instead of blindly dropping the newest
+      const dropped = wQueue.shift(); // removes oldest
+      if (dropped) {
+        const ageMs = Date.now() - dropped.detectedAt.getTime();
+        logger.warn(`[BoundedTransactionQueue] BACKPRESSURE (Wallet ${item.walletAddress}): queue full. Dropped oldest signature: ${dropped.signature}. Appending newest: ${item.signature}`);
+        if (this.metricsProvider) {
+          this.metricsProvider.recordDroppedOldestCount(item.walletAddress);
+        }
+        dropped.onFailure(new BackpressureDropError(
+          'Dropped from queue due to backpressure',
+          dropped.walletAddress,
+          dropped.signature,
+          wQueue.length + 1, // depth when drop occurred
+          ageMs
+        )).catch(() => {});
+      }
+    }
+
+    wQueue.push(item);
+
+    // Track oldest queued item age in metrics
+    if (this.metricsProvider && wQueue.length > 0 && wQueue[0]) {
+      this.metricsProvider.recordOldestQueuedAge(item.walletAddress, Date.now() - wQueue[0].detectedAt.getTime());
+      this.metricsProvider.recordWalletQueueDepth(item.walletAddress, wQueue.length);
+      this.metricsProvider.recordQueueDepth(this.getDepth());
+    }
+
+    // Ensure wallet is in round-robin scheduler order
+    if (!this.walletOrder.includes(item.walletAddress)) {
+      this.walletOrder.push(item.walletAddress);
+    }
+
+    logger.debug(`[BoundedTransactionQueue] Queued signature ${item.signature} for wallet ${item.walletAddress}. Depth: ${wQueue.length}`);
+
+    // Trigger process next non-blockingly
+    this.processNext();
+    return true;
+  }
+
+  private async processNext(): Promise<void> {
+    if (!this.running) return;
+    if (this.activeCount >= this.maxConcurrency) return;
+
+    // Filter out empty queues from round robin orders
+    this.walletOrder = this.walletOrder.filter(addr => {
+      const q = this.walletQueues.get(addr);
+      return q && q.length > 0;
+    });
+
+    if (this.walletOrder.length === 0) return;
+
+    // Enforcement of rate limiting delay
+    const now = Date.now();
+    const timeSinceLast = now - this.lastRequestTime;
+    if (timeSinceLast < this.minDelayMs) {
+      const waitTime = this.minDelayMs - timeSinceLast;
+      if (!this.rateLimitTimeout) {
+        logger.debug(`[BoundedTransactionQueue] Global rate limit: waiting ${waitTime}ms`);
+        this.rateLimitTimeout = setTimeout(() => {
+          this.rateLimitTimeout = null;
+          this.processNext();
+        }, waitTime);
+      }
+      return;
+    }
+
+    // Fair round-robin: pull the first wallet address from scheduling list
+    const walletAddr = this.walletOrder.shift();
+    if (!walletAddr) return;
+
+    const wQueue = this.walletQueues.get(walletAddr);
+    if (!wQueue || wQueue.length === 0) return;
+
+    const item = wQueue.shift();
+    if (!item) return;
+
+    // Re-queue the wallet address at the end of the order if it still has pending items
+    if (wQueue.length > 0) {
+      this.walletOrder.push(walletAddr);
+    }
+
+    if (this.metricsProvider) {
+      this.metricsProvider.recordWalletQueueDepth(walletAddr, wQueue.length);
+      this.metricsProvider.recordQueueDepth(this.getDepth());
+    }
+
+    this.activeCount++;
+    this.lastRequestTime = Date.now();
+    this.requestCountLastSecond++;
+
+    logger.debug(`[BoundedTransactionQueue] Executing item ${item.signature} from fair wallet ${walletAddr}. Active: ${this.activeCount}/${this.maxConcurrency}`);
+
+    // Asynchronously trigger fetch
+    this.executeFetch(item);
+
+    // Concurrently try triggering others
+    this.processNext();
+  }
+
+  private async executeFetch(item: QueueItem): Promise<void> {
+    const fetchStartTime = Date.now();
+    try {
+      const tx = await fetchTransactionWithRetry(
+        this.connection,
+        item.signature,
+        5,
+        500,
+        4000,
+        this.metricsProvider,
+      );
+
+      const fetchEndTime = Date.now();
+      const fetchDuration = fetchEndTime - fetchStartTime;
+
+      if (this.metricsProvider) {
+        this.metricsProvider.recordQuoteLatency(fetchDuration, 'rpc_fetch');
+        this.metricsProvider.recordQueueProcessed(item.walletAddress);
+      }
+
+      await item.onSuccess(tx);
+    } catch (err: any) {
+      logger.error(`[BoundedTransactionQueue] Processing failed for signature ${item.signature}`, err);
+      if (this.metricsProvider) {
+        this.metricsProvider.recordRpcFetchError(item.walletAddress);
+      }
+      await item.onFailure(err);
+    } finally {
+      this.activeCount--;
+      logger.debug(`[BoundedTransactionQueue] Finished item ${item.signature}. Active: ${this.activeCount}`);
+      this.processNext();
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/solana/parser.ts b/src/solana/parser.ts
new file mode 100644
index 0000000..33c21d6
--- /dev/null
+++ b/src/solana/parser.ts
@@ -0,0 +1,140 @@
+import { VersionedTransactionResponse } from '@solana/web3.js';
+
+export interface WalletBalanceChanges {
+  solChange: bigint;
+  tokenChanges: { mint: string; change: bigint }[];
+}
+
+export function getAccountKeysArray(tx: VersionedTransactionResponse): any[] {
+  const message = tx.transaction.message;
+  if (!message) {
+    throw new Error('Transaction message is missing or unresolvable');
+  }
+
+  // Extract static account keys
+  let staticKeys: any[] = [];
+  if (typeof (message as any).getAccountKeys === 'function') {
+    try {
+      const keys = (message as any).getAccountKeys();
+      if (keys && Array.isArray(keys.staticAccountKeys)) {
+        staticKeys = keys.staticAccountKeys;
+      } else if (Array.isArray(keys)) {
+        staticKeys = keys;
+      }
+    } catch {
+      // fallback to raw fields
+    }
+  }
+
+  if (staticKeys.length === 0) {
+    if (Array.isArray((message as any).staticAccountKeys)) {
+      staticKeys = (message as any).staticAccountKeys;
+    } else if (Array.isArray((message as any).accountKeys)) {
+      staticKeys = (message as any).accountKeys;
+    } else {
+      throw new Error('Failed to resolve static account keys from transaction message');
+    }
+  }
+
+  // Extract loaded addresses from meta
+  let loadedWritable: any[] = [];
+  let loadedReadonly: any[] = [];
+
+  if (tx.meta?.loadedAddresses) {
+    if (Array.isArray(tx.meta.loadedAddresses.writable)) {
+      loadedWritable = tx.meta.loadedAddresses.writable;
+    }
+    if (Array.isArray(tx.meta.loadedAddresses.readonly)) {
+      loadedReadonly = tx.meta.loadedAddresses.readonly;
+    }
+  }
+
+  return [...staticKeys, ...loadedWritable, ...loadedReadonly];
+}
+
+export function calculateBalanceChanges(
+  tx: VersionedTransactionResponse,
+  walletAddress: string,
+): WalletBalanceChanges {
+  const accountKeys = getAccountKeysArray(tx);
+  let walletIndex = -1;
+
+  for (let i = 0; i < accountKeys.length; i++) {
+    const addr = accountKeys[i];
+    const addrStr = addr && typeof addr.toBase58 === 'function' ? addr.toBase58() : String(addr);
+    if (addrStr === walletAddress) {
+      walletIndex = i;
+      break;
+    }
+  }
+
+  let solChange = 0n;
+  if (walletIndex !== -1 && tx.meta) {
+    const preBalances = tx.meta.preBalances || [];
+    const postBalances = tx.meta.postBalances || [];
+    const preVal = preBalances[walletIndex];
+    const postVal = postBalances[walletIndex];
+    const pre = preVal !== undefined && preVal !== null ? BigInt(preVal) : 0n;
+    const post = postVal !== undefined && postVal !== null ? BigInt(postVal) : 0n;
+    solChange = post - pre;
+  }
+
+  const tokenChanges: { mint: string; change: bigint }[] = [];
+  if (tx.meta) {
+    const preTokenBalances = tx.meta.preTokenBalances || [];
+    const postTokenBalances = tx.meta.postTokenBalances || [];
+
+    const preMap = new Map<string, bigint>();
+    for (const item of preTokenBalances) {
+      const owner = item.owner || (walletIndex !== -1 && item.accountIndex === walletIndex ? walletAddress : '');
+      if (owner === walletAddress && item.mint && item.uiTokenAmount.amount) {
+        const val = BigInt(item.uiTokenAmount.amount);
+        preMap.set(item.mint, (preMap.get(item.mint) || 0n) + val);
+      }
+    }
+
+    const postMap = new Map<string, bigint>();
+    for (const item of postTokenBalances) {
+      const owner = item.owner || (walletIndex !== -1 && item.accountIndex === walletIndex ? walletAddress : '');
+      if (owner === walletAddress && item.mint && item.uiTokenAmount.amount) {
+        const val = BigInt(item.uiTokenAmount.amount);
+        postMap.set(item.mint, (postMap.get(item.mint) || 0n) + val);
+      }
+    }
+
+    const allMints = new Set([...preMap.keys(), ...postMap.keys()]);
+    for (const mint of allMints) {
+      const preAmt = preMap.get(mint) || 0n;
+      const postAmt = postMap.get(mint) || 0n;
+      const diff = postAmt - preAmt;
+      if (diff !== 0n) {
+        tokenChanges.push({ mint, change: diff });
+      }
+    }
+  }
+
+  return {
+    solChange,
+    tokenChanges,
+  };
+}
+
+export function isTransactionRelevant(
+  tx: VersionedTransactionResponse,
+  walletAddress: string,
+): boolean {
+  const { solChange, tokenChanges } = calculateBalanceChanges(tx, walletAddress);
+
+  // Sol change is meaningful if it is not just fee (or 0)
+  // Fees are typically very small, e.g., < 0.005 SOL (5,000,000 lamports)
+  // Let's check if the native SOL absolute balance change is greater than a standard transaction fee
+  // 50,000 lamports is the absolute minimum, let's use 10,000,000 lamports (0.01 SOL) to be robustly conservative,
+  // or simple rule: if absolute solChange is greater than 1,000,000 lamports (0.001 SOL), it's a real transfer/swap.
+  const absSolChange = solChange < 0n ? -solChange : solChange;
+  const meaningfulSol = absSolChange > 1_000_000n; // > 0.001 SOL change
+
+  // Token change is meaningful if any token change absolute value > 0
+  const meaningfulToken = tokenChanges.length > 0;
+
+  return meaningfulSol || meaningfulToken;
+}
diff --git a/tests/realMode.test.ts b/tests/realMode.test.ts
index 3053580..cabf16f 100644
--- a/tests/realMode.test.ts
+++ b/tests/realMode.test.ts
@@ -36,6 +36,23 @@ vi.mock('@solana/web3.js', () => {
   };
 });
 
+// Mock database interactions to avoid live connections
+vi.mock('../src/persistence/db.js', () => {
+  return {
+    initDb: vi.fn(),
+    verifyDbHealth: vi.fn().mockResolvedValue(undefined),
+    closeDb: vi.fn().mockResolvedValue(undefined),
+    getDbPool: vi.fn().mockImplementation(() => {
+      return {
+        query: vi.fn().mockResolvedValue({
+          rows: [{ id: 'mock-id', address: '3yF9asA9B7G3Y1G7as78gHJKa7A', name: 'Mock Wallet', is_active: true, created_at: new Date(), updated_at: new Date() }],
+          rowCount: 1,
+        }),
+      };
+    }),
+  };
+});
+
 describe('Real Solana Observation Mode Unit Tests', () => {
   let connection: any;
 
@@ -291,4 +308,626 @@ describe('Real Solana Observation Mode Unit Tests', () => {
       expect(events.map((e) => e.eventType)).toContain('raw_transaction_fetch_failed');
     });
   });
+
+  describe('BoundedTransactionQueue Unit Tests', () => {
+    let mockMetrics: any;
+
+    beforeEach(() => {
+      mockMetrics = {
+        recordQueueDepth: vi.fn(),
+        recordQueueRetries: vi.fn(),
+        recordQueue429s: vi.fn(),
+        recordQuoteLatency: vi.fn(),
+        recordSignalProcessingLatency: vi.fn(),
+        recordWalletEventReceived: vi.fn(),
+        recordWalletQueueDepth: vi.fn(),
+        recordOldestQueuedAge: vi.fn(),
+        recordDroppedOldestCount: vi.fn(),
+        recordTransactionRelevance: vi.fn(),
+        recordRpcRequestRate: vi.fn(),
+        recordQueueProcessed: vi.fn(),
+        recordRpcFetchError: vi.fn(),
+      };
+    });
+
+    it('should respect max concurrency limit and rate limiting delay', async () => {
+      const { BoundedTransactionQueue } = await import('../src/solana/fetcher.js');
+      const mockTx = { slot: 100, blockTime: 123456 };
+      connection.getTransaction.mockResolvedValue(mockTx);
+
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        2,    // maxConcurrency = 2
+        100,  // minDelayMs = 100ms
+        10,   // maxQueueSize = 10
+        mockMetrics,
+      );
+      queue.start();
+
+      const successSigs: string[] = [];
+      const pushItem = (sig: string) => {
+        return new Promise<void>((resolve) => {
+          queue.push({
+            signature: sig,
+            walletAddress: 'wallet1',
+            slot: 100,
+            detectedAt: new Date(),
+            correlationId: 'corr',
+            onSuccess: async () => {
+              successSigs.push(sig);
+              resolve();
+            },
+            onFailure: async () => {
+              resolve();
+            },
+          });
+        });
+      };
+
+      // Push 3 items concurrently
+      const p1 = pushItem('sig1');
+      const p2 = pushItem('sig2');
+      const p3 = pushItem('sig3');
+
+      // Check that at most 2 are active initially
+      expect(queue.getActiveCount()).toBeLessThanOrEqual(2);
+
+      await Promise.all([p1, p2, p3]);
+
+      expect(successSigs).toContain('sig1');
+      expect(successSigs).toContain('sig2');
+      expect(successSigs).toContain('sig3');
+      expect(queue.getDepth()).toBe(0);
+      expect(queue.getActiveCount()).toBe(0);
+
+      queue.stop();
+    });
+
+    it('should drop incoming items and apply backpressure when queue size is exceeded', async () => {
+      const { BoundedTransactionQueue } = await import('../src/solana/fetcher.js');
+      const mockTx = { slot: 100, blockTime: 123456 };
+      connection.getTransaction.mockResolvedValue(mockTx);
+
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        1,   // maxConcurrency = 1
+        100, // minDelay = 100
+        2,   // maxQueueSize = 2 (allows 2 items to wait in queue)
+      );
+      queue.start();
+
+      const results: string[] = [];
+      const errors: string[] = [];
+
+      const pushItem = (sig: string) => {
+        queue.push({
+          signature: sig,
+          walletAddress: 'wallet1',
+          slot: 100,
+          detectedAt: new Date(),
+          correlationId: 'corr',
+          onSuccess: async () => {
+            results.push(sig);
+          },
+          onFailure: async (err) => {
+            errors.push(`${sig}:${err.message}`);
+          },
+        });
+      };
+
+      // Push 4 items (concurrency=1, max queue=2 -> 1 active, 2 in queue, 4th item triggers drop-oldest of item2)
+      pushItem('item1'); // goes active immediately (active=1, queue=[])
+      pushItem('item2'); // queued (active=1, queue=[item2])
+      pushItem('item3'); // queued (active=1, queue=[item2, item3])
+      pushItem('item4'); // queue full! item2 is dropped, queue becomes [item3, item4]
+
+      expect(errors).toContain('item2:Dropped from queue due to backpressure');
+      
+      queue.stop();
+    });
+
+    it('should implement HTTP 429 exponential backoff with jitter and successfully retry', async () => {
+      const mockTx = { slot: 100, blockTime: 123456 };
+      // First attempt triggers HTTP 429 rate limit error
+      const rateLimitErr = { status: 429, message: 'Too Many Requests' };
+      connection.getTransaction
+        .mockRejectedValueOnce(rateLimitErr)
+        .mockResolvedValueOnce(mockTx);
+
+      const result = await fetchTransactionWithRetry(connection as any, 'sig-429', 3, 10, 50, mockMetrics);
+      expect(result).toEqual(mockTx);
+      expect(connection.getTransaction).toHaveBeenCalledTimes(2);
+      expect(mockMetrics.recordQueue429s).toHaveBeenCalledWith('sig-429');
+    });
+
+    it('should gracefully drain or terminate the queue when stopped during graceful shutdown', async () => {
+      const { BoundedTransactionQueue } = await import('../src/solana/fetcher.js');
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        1,
+        100,
+        10,
+      );
+      queue.start();
+
+      let failed = false;
+      queue.push({
+        signature: 'sig-drain',
+        walletAddress: 'wallet',
+        slot: 100,
+        detectedAt: new Date(),
+        correlationId: 'corr',
+        onSuccess: async () => {},
+        onFailure: async () => {
+          failed = true;
+        },
+      });
+
+      expect(queue.getDepth()).toBe(0); // goes to active immediately
+      queue.stop();
+
+      // Pushing after stop must fail immediately
+      const pushedAfter = queue.push({
+        signature: 'sig-after',
+        walletAddress: 'wallet',
+        slot: 100,
+        detectedAt: new Date(),
+        correlationId: 'corr',
+        onSuccess: async () => {},
+        onFailure: async () => {
+          failed = true;
+        },
+      });
+
+      expect(pushedAfter).toBe(false);
+      expect(failed).toBe(true);
+    });
+
+    it('should correctly schedule high-volume wallet without starving another wallet (fair round robin)', async () => {
+      const { BoundedTransactionQueue } = await import('../src/solana/fetcher.js');
+      const mockTx = { slot: 100, blockTime: 123456 };
+      connection.getTransaction.mockResolvedValue(mockTx);
+
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        1,  // maxConcurrency = 1
+        10, // minDelay = 10ms
+        10, // max size per-wallet
+      );
+      queue.start();
+
+      const successOrder: string[] = [];
+
+      const pushItem = (sig: string, wallet: string) => {
+        queue.push({
+          signature: sig,
+          walletAddress: wallet,
+          slot: 100,
+          detectedAt: new Date(),
+          correlationId: 'corr',
+          onSuccess: async () => {
+            successOrder.push(sig);
+          },
+          onFailure: async () => {},
+        });
+      };
+
+      // Push A1. It executes immediately.
+      pushItem('A1', 'walletA'); // activeCount=1, walletOrder=[]
+
+      // Now enqueue additional tasks.
+      // A2 is pushed. It goes to 'walletA' queue. walletOrder becomes ['walletA']
+      pushItem('A2', 'walletA'); 
+      // A3 is pushed. It goes to 'walletA' queue. Since 'walletA' is already in walletOrder, order remains ['walletA']
+      pushItem('A3', 'walletA');
+      // B1 is pushed. It goes to 'walletB' queue. walletOrder becomes ['walletA', 'walletB']
+      pushItem('B1', 'walletB');
+
+      // Now A1 finishes. processNext() is called.
+      // It retrieves from scheduling order: 'walletOrder.shift()' -> yields 'walletA'!
+      // So 'A2' is dequeued and executed next.
+      // Since 'walletA' still has 'A3', it is re-queued at the back of the order.
+      // walletOrder becomes: ['walletB', 'walletA']
+      // 
+      // Then A2 finishes. processNext() is called.
+      // It shifts 'walletOrder' -> yields 'walletB'!
+      // So 'B1' is dequeued and executed third.
+      // 
+      // Finally B1 finishes. processNext() shifts -> yields 'walletA' -> executes 'A3'.
+      //
+      // Hence successOrder will be: ['A1', 'A2', 'B1', 'A3']
+      // This proves B1 is scheduled fairly and is NOT starved by A3 even though A was queued first!
+
+      // Process and wait for all tasks to settle
+      await new Promise((resolve) => setTimeout(resolve, 150));
+
+      expect(successOrder[0]).toBe('A1');
+      expect(successOrder[1]).toBe('A2'); 
+      expect(successOrder[2]).toBe('B1'); // Fair scheduling ensures B1 executes third, before A3!
+      expect(successOrder[3]).toBe('A3');
+
+      queue.stop();
+    });
+
+    it('should drop oldest items and preserve newest events under backpressure', async () => {
+      const { BoundedTransactionQueue } = await import('../src/solana/fetcher.js');
+      const mockTx = { slot: 100, blockTime: 123456 };
+      connection.getTransaction.mockResolvedValue(mockTx);
+
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        1,   // maxConcurrency = 1
+        50,  // minDelay = 50ms
+        2,   // max queue size per-wallet = 2
+      );
+      queue.start();
+
+      const results: string[] = [];
+      const errors: string[] = [];
+
+      const pushItem = (sig: string) => {
+        queue.push({
+          signature: sig,
+          walletAddress: 'wallet1',
+          slot: 100,
+          detectedAt: new Date(),
+          correlationId: 'corr',
+          onSuccess: async () => {
+            results.push(sig);
+          },
+          onFailure: async (err) => {
+            errors.push(`${sig}:${err.message}`);
+          },
+        });
+      };
+
+      pushItem('T1'); // Runs immediately
+      pushItem('T2'); // Queued (pos 0)
+      pushItem('T3'); // Queued (pos 1)
+      pushItem('T4'); // Queued full! Drops oldest ('T2'), appends T4. Queue is now: [T3, T4]
+
+      expect(errors).toContain('T2:Dropped from queue due to backpressure');
+
+      await new Promise((resolve) => setTimeout(resolve, 200));
+
+      expect(results).toContain('T1');
+      expect(results).not.toContain('T2'); // dropped
+      expect(results).toContain('T3');
+      expect(results).toContain('T4'); // newest preserved!
+
+      queue.stop();
+    });
+
+    it('should prove backpressure drop is not reported as fetch failure, generates no stack trace, and metrics distinguish it', async () => {
+      const { BoundedTransactionQueue, BackpressureDropError } = await import('../src/solana/fetcher.js');
+      const { logger } = await import('../src/logging/index.js');
+      const loggerWarnSpy = vi.spyOn(logger, 'warn');
+      const loggerErrorSpy = vi.spyOn(logger, 'error');
+
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        1,   // maxConcurrency = 1
+        10,  // minDelay = 10ms
+        1,   // max queue size per-wallet = 1
+        mockMetrics,
+      );
+      queue.start();
+
+      let capturedError: any = null;
+
+      queue.push({
+        signature: 'T1',
+        walletAddress: 'wallet1',
+        slot: 100,
+        detectedAt: new Date(),
+        correlationId: 'corr1',
+        onSuccess: async () => {},
+        onFailure: async () => {},
+      });
+
+      queue.push({
+        signature: 'T2',
+        walletAddress: 'wallet1',
+        slot: 100,
+        detectedAt: new Date(),
+        correlationId: 'corr2',
+        onSuccess: async () => {},
+        onFailure: async (err) => {
+          capturedError = err;
+        },
+      });
+
+      // T3 will trigger drop of T2
+      queue.push({
+        signature: 'T3',
+        walletAddress: 'wallet1',
+        slot: 100,
+        detectedAt: new Date(),
+        correlationId: 'corr3',
+        onSuccess: async () => {},
+        onFailure: async () => {},
+      });
+
+      expect(capturedError).toBeInstanceOf(BackpressureDropError);
+      expect(capturedError.stack).toBeUndefined();
+
+      // Verify that backpressure drop logs WARN, not ERROR
+      const backpressureWarns = loggerWarnSpy.mock.calls.filter(call => 
+        call[0] && call[0].includes('BACKPRESSURE')
+      );
+      expect(backpressureWarns.length).toBeGreaterThan(0);
+
+      const backpressureErrors = loggerErrorSpy.mock.calls.filter(call =>
+        call[0] && call[0].includes('BACKPRESSURE')
+      );
+      expect(backpressureErrors.length).toBe(0);
+
+      // Verify operational metrics: recordDroppedOldestCount called, recordRpcFetchError NOT called
+      expect(mockMetrics.recordDroppedOldestCount).toHaveBeenCalledWith('wallet1');
+      expect(mockMetrics.recordRpcFetchError).not.toHaveBeenCalled();
+
+      queue.stop();
+      loggerWarnSpy.mockRestore();
+      loggerErrorSpy.mockRestore();
+    });
+
+    it('should prove one rate-limit wait produces only one scheduling/log event and does not spam logs', async () => {
+      const { BoundedTransactionQueue } = await import('../src/solana/fetcher.js');
+      const { logger } = await import('../src/logging/index.js');
+      const loggerDebugSpy = vi.spyOn(logger, 'debug');
+
+      const queue = new BoundedTransactionQueue(
+        connection as any,
+        1,   // maxConcurrency = 1
+        1000, // minDelay = 1000ms (so we trigger rate limit)
+        10,  // max queue size per-wallet = 10
+        mockMetrics,
+      );
+      queue.start();
+
+      // Push item 1 (executed immediately, updates lastRequestTime)
+      queue.push({
+        signature: 'R1',
+        walletAddress: 'wallet1',
+        slot: 100,
+        detectedAt: new Date(),
+        correlationId: 'corr1',
+        onSuccess: async () => {},
+        onFailure: async () => {},
+      });
+
+      // Push 5 more items concurrently (within rate-limit interval)
+      for (let i = 2; i <= 6; i++) {
+        queue.push({
+          signature: `R${i}`,
+          walletAddress: 'wallet1',
+          slot: 100,
+          detectedAt: new Date(),
+          correlationId: `corr${i}`,
+          onSuccess: async () => {},
+          onFailure: async () => {},
+        });
+      }
+
+      // Wait for R1 to finish and trigger the rate limit wait
+      await new Promise((resolve) => setTimeout(resolve, 50));
+
+      // Check the debug logs for "Global rate limit: waiting"
+      const rateLimitDebugs = loggerDebugSpy.mock.calls.filter(call =>
+        call[0] && call[0].includes('Global rate limit: waiting')
+      );
+
+      // Even with 5 pushes under rate limit, we should only have ONE rate limit waiting log event
+      expect(rateLimitDebugs.length).toBe(1);
+
+      queue.stop();
+      loggerDebugSpy.mockRestore();
+    });
+
+    it('should classify fetched transactions correctly based on SOL/SPL token balance changes', async () => {
+      const { isTransactionRelevant } = await import('../src/solana/parser.js');
+
+      // 1. Irrelevant payload (no balance changes or only extremely tiny SOL shift simulating fee)
+      const irrelevantTx: any = {
+        transaction: {
+          message: {
+            getAccountKeys: () => ({
+              staticAccountKeys: [{ toBase58: () => 'my-wallet' }],
+            }),
+          },
+        },
+        meta: {
+          preBalances: [1000000000n],
+          postBalances: [1000000000n], // exactly 0 change
+          preTokenBalances: [],
+          postTokenBalances: [],
+        },
+      };
+
+      // 2. Meaningful SOL transfer payload
+      const relevantSolTx: any = {
+        transaction: {
+          message: {
+            getAccountKeys: () => ({
+              staticAccountKeys: [{ toBase58: () => 'my-wallet' }],
+            }),
+          },
+        },
+        meta: {
+          preBalances: [1000000000],
+          postBalances: [900000000], // -100,000,000 lamports (-0.1 SOL) change
+          preTokenBalances: [],
+          postTokenBalances: [],
+        },
+      };
+
+      // 3. Meaningful SPL Token swap payload
+      const relevantTokenTx: any = {
+        transaction: {
+          message: {
+            getAccountKeys: () => ({
+              staticAccountKeys: [{ toBase58: () => 'my-wallet' }],
+            }),
+          },
+        },
+        meta: {
+          preBalances: [1000000000],
+          postBalances: [1000000000], // 0 SOL change
+          preTokenBalances: [
+            { owner: 'my-wallet', mint: 'token-mint-1', uiTokenAmount: { amount: '1000' } },
+          ],
+          postTokenBalances: [
+            { owner: 'my-wallet', mint: 'token-mint-1', uiTokenAmount: { amount: '5000' } }, // +4000 change
+          ],
+        },
+      };
+
+      expect(isTransactionRelevant(irrelevantTx, 'my-wallet')).toBe(false);
+      expect(isTransactionRelevant(relevantSolTx, 'my-wallet')).toBe(true);
+      expect(isTransactionRelevant(relevantTokenTx, 'my-wallet')).toBe(true);
+    });
+
+    it('should correctly resolve accounts and relevance for legacy transactions', async () => {
+      const { isTransactionRelevant } = await import('../src/solana/parser.js');
+
+      const legacyTx: any = {
+        transaction: {
+          message: {
+            accountKeys: [{ toBase58: () => 'my-wallet' }, { toBase58: () => 'other-acct' }],
+          },
+        },
+        meta: {
+          preBalances: [2000000000, 50000000],
+          postBalances: [1000000000, 105000000], // SOL shift: -1 SOL for my-wallet (relevant)
+          preTokenBalances: [],
+          postTokenBalances: [],
+        },
+      };
+
+      expect(isTransactionRelevant(legacyTx, 'my-wallet')).toBe(true);
+      expect(isTransactionRelevant(legacyTx, 'other-acct')).toBe(true);
+    });
+
+    it('should correctly resolve accounts and relevance for v0 transactions without address lookup tables', async () => {
+      const { isTransactionRelevant } = await import('../src/solana/parser.js');
+
+      const v0TxWithoutAlts: any = {
+        transaction: {
+          message: {
+            staticAccountKeys: [{ toBase58: () => 'my-wallet' }, { toBase58: () => 'other-acct' }],
+          },
+        },
+        meta: {
+          preBalances: [1000000000, 50000000],
+          postBalances: [1000000000, 50000000], // no SOL shift
+          preTokenBalances: [
+            { owner: 'my-wallet', mint: 'token-mint-v0', uiTokenAmount: { amount: '10' } }
+          ],
+          postTokenBalances: [
+            { owner: 'my-wallet', mint: 'token-mint-v0', uiTokenAmount: { amount: '110' } } // relevant SPL shift
+          ],
+        },
+      };
+
+      expect(isTransactionRelevant(v0TxWithoutAlts, 'my-wallet')).toBe(true);
+    });
+
+    it('should correctly resolve accounts and relevance for v0 transactions with loaded addresses (ALTs)', async () => {
+      const { isTransactionRelevant, getAccountKeysArray } = await import('../src/solana/parser.js');
+
+      const v0TxWithAlts: any = {
+        transaction: {
+          message: {
+            staticAccountKeys: [{ toBase58: () => 'static-1' }],
+          },
+        },
+        meta: {
+          loadedAddresses: {
+            writable: [{ toBase58: () => 'loaded-writable-1' }],
+            readonly: [{ toBase58: () => 'loaded-readonly-1' }, { toBase58: () => 'loaded-readonly-2' }]
+          },
+          preBalances: [5000000000, 1000000000, 50000000, 50000000],
+          postBalances: [4900000000, 1100000000, 50000000, 50000000], // transfer 0.1 SOL from static-1 to loaded-writable-1
+          preTokenBalances: [],
+          postTokenBalances: [],
+        },
+      };
+
+      // Verify full index mapping: 
+      // 0 -> static-1, 1 -> loaded-writable-1, 2 -> loaded-readonly-1, 3 -> loaded-readonly-2
+      const keys = getAccountKeysArray(v0TxWithAlts).map(k => k.toBase58());
+      expect(keys).toEqual(['static-1', 'loaded-writable-1', 'loaded-readonly-1', 'loaded-readonly-2']);
+
+      // static-1 had post-pre = 4.9B - 5B = -100M lamports (relevant SOL change)
+      expect(isTransactionRelevant(v0TxWithAlts, 'static-1')).toBe(true);
+
+      // loaded-writable-1 had post-pre = 1.1B - 1B = 100M lamports (relevant SOL change)
+      expect(isTransactionRelevant(v0TxWithAlts, 'loaded-writable-1')).toBe(true);
+
+      // loaded-readonly-1 had post-pre = 50M - 50M = 0 lamports (irrelevant)
+      expect(isTransactionRelevant(v0TxWithAlts, 'loaded-readonly-1')).toBe(false);
+    });
+
+    it('should throw an error on account resolution or parsing failures as a distinct error state', async () => {
+      const { isTransactionRelevant } = await import('../src/solana/parser.js');
+
+      const malformedTx: any = {
+        transaction: {
+          // message is missing
+        },
+      };
+
+      await expect(async () => {
+        isTransactionRelevant(malformedTx, 'any-wallet');
+      }).rejects.toThrow('Transaction message is missing or unresolvable');
+    });
+  });
+
+  describe('Application Real Mode vs Mock Mode Loop Behavior', () => {
+    it('should NOT start SimulationScheduler processing loop in real mode and keep pending simulated executions untouched', async () => {
+      const oldMode = process.env.WALLET_WATCHER_MODE;
+      process.env.WALLET_WATCHER_MODE = 'real';
+      process.env.WATCHED_WALLETS = '3yF9asA9B7G3Y1G7as78gHJKa7A';
+
+      try {
+        const { Application } = await import('../src/application/index.js');
+        const app = new Application();
+        await app.bootstrap();
+
+        // Proves that no interval id was created/started for the simulated loop
+        expect(app.simulationIntervalId).toBeNull();
+
+        await app.shutdown('SIGINT');
+      } finally {
+        if (oldMode) {
+          process.env.WALLET_WATCHER_MODE = oldMode;
+        } else {
+          delete process.env.WALLET_WATCHER_MODE;
+        }
+      }
+    });
+
+    it('should start SimulationScheduler processing loop in mock mode', async () => {
+      const oldMode = process.env.WALLET_WATCHER_MODE;
+      process.env.WALLET_WATCHER_MODE = 'mock';
+      process.env.WATCHED_WALLETS = '3yF9asA9B7G3Y1G7as78gHJKa7A';
+
+      try {
+        const { Application } = await import('../src/application/index.js');
+        const app = new Application();
+        await app.bootstrap();
+
+        // Proves that interval id WAS started for the simulated loop
+        expect(app.simulationIntervalId).not.toBeNull();
+
+        await app.shutdown('SIGINT');
+      } finally {
+        if (oldMode) {
+          process.env.WALLET_WATCHER_MODE = oldMode;
+        } else {
+          delete process.env.WALLET_WATCHER_MODE;
+        }
+      }
+    });
+  });
 });