diff --git a/listener/src/config.test.ts b/listener/src/config.test.ts
index 7b7ec70..3ffb85b 100644
--- a/listener/src/config.test.ts
+++ b/listener/src/config.test.ts
@@ -56,6 +56,8 @@ describe('Config validation', () => {
     delete process.env.RETRY_MAX_RETRIES;
     delete process.env.DISCORD_WEBHOOK_URL;
     delete process.env.DISCORD_WEBHOOK_ID;
+    delete process.env.NOTIFICATION_DEDUPLICATION_WINDOW_MS;
+    delete process.env.NOTIFICATION_DEDUPLICATION_MAX_SIZE;
 
     const config = loadConfig();
 
@@ -74,4 +76,20 @@ describe('Config validation', () => {
       },
     });
   });
+
+  it('loads notification deduplication settings when Discord is configured', () => {
+    process.env.DISCORD_WEBHOOK_URL = 'https://discord.com/api/webhooks/123/abc';
+    process.env.DISCORD_WEBHOOK_ID = '123';
+    process.env.NOTIFICATION_DEDUPLICATION_WINDOW_MS = '15000';
+    process.env.NOTIFICATION_DEDUPLICATION_MAX_SIZE = '250';
+
+    const config = loadConfig();
+
+    expect(config.discord).toMatchObject({
+      webhookUrl: 'https://discord.com/api/webhooks/123/abc',
+      webhookId: '123',
+      deduplicationWindowMs: 15000,
+      deduplicationMaxSize: 250,
+    });
+  });
 });
diff --git a/listener/src/config.ts b/listener/src/config.ts
index 455168c..103d830 100644
--- a/listener/src/config.ts
+++ b/listener/src/config.ts
@@ -77,7 +77,12 @@ function loadDiscordConfig(): DiscordConfig | undefined {
     throw new ConfigError('DISCORD_WEBHOOK_ID is required when DISCORD_WEBHOOK_URL is provided.');
   }
 
-  return { webhookUrl, webhookId };
+  return {
+    webhookUrl,
+    webhookId,
+    deduplicationWindowMs: parseIntegerEnv('NOTIFICATION_DEDUPLICATION_WINDOW_MS', '60000'),
+    deduplicationMaxSize: parseIntegerEnv('NOTIFICATION_DEDUPLICATION_MAX_SIZE', '10000'),
+  };
 }
 
 export function loadConfig(): Config {
@@ -101,3 +106,4 @@ export function loadConfig(): Config {
     },
   };
 }
+
diff --git a/listener/src/services/discord-notification.test.ts b/listener/src/services/discord-notification.test.ts
index c866716..2746792 100644
--- a/listener/src/services/discord-notification.test.ts
+++ b/listener/src/services/discord-notification.test.ts
@@ -106,7 +106,10 @@ describe('DiscordNotificationService', () => {
       const secondResult = await service.sendEventNotification(mockEvent, mockContractConfig);
 
       expect(mockFetch).toHaveBeenCalledTimes(1);
-      expect(secondResult).toBe(false);
+      expect(secondResult).toBe(true);
+      expect(service.getDeduplicationMetrics()).toEqual(
+        expect.objectContaining({ skippedDuplicates: 1, cacheSize: 1 })
+      );
     });
 
     it('logs a duplicate detection event', async () => {
@@ -129,6 +132,27 @@ describe('DiscordNotificationService', () => {
       );
     });
 
+
+    it('allows the same notification request after the configured window expires', async () => {
+      mockFetch.mockResolvedValue({ ok: true });
+      let now = 1000;
+      const deduplicator = new NotificationDeduplicator({ windowMs: 500, now: () => now });
+      const service = new DiscordNotificationService(mockConfig, deduplicator);
+      const mockEvent = createMockEvent({ id: 'event-windowed' });
+      const mockContractConfig = { address: 'CA123', events: ['test'] };
+
+      await service.sendEventNotification(mockEvent, mockContractConfig);
+      await service.sendEventNotification(mockEvent, mockContractConfig);
+      now = 1501;
+      const result = await service.sendEventNotification(mockEvent, mockContractConfig);
+
+      expect(result).toBe(true);
+      expect(mockFetch).toHaveBeenCalledTimes(2);
+      expect(service.getDeduplicationMetrics()).toEqual(
+        expect.objectContaining({ acceptedRequests: 2, skippedDuplicates: 1 })
+      );
+    });
+
     it('allows the same event id on a different contract through', async () => {
       mockFetch.mockResolvedValue({ ok: true });
 
@@ -253,4 +277,4 @@ describe('DiscordNotificationService', () => {
       expect(valueField.value).toContain('my_symbol');
     });
   });
-});
\ No newline at end of file
+});
diff --git a/listener/src/services/discord-notification.ts b/listener/src/services/discord-notification.ts
index 4af1f40..2c764ff 100644
--- a/listener/src/services/discord-notification.ts
+++ b/listener/src/services/discord-notification.ts
@@ -28,7 +28,12 @@ export class DiscordNotificationService {
 
   constructor(config: DiscordConfig, deduplicator?: NotificationDeduplicator) {
     this.config = config;
-    this.deduplicator = deduplicator ?? new NotificationDeduplicator();
+    this.deduplicator =
+      deduplicator ??
+      new NotificationDeduplicator({
+        windowMs: config.deduplicationWindowMs,
+        maxSize: config.deduplicationMaxSize,
+      });
   }
 
   async sendEventNotification(
@@ -43,8 +48,9 @@ export class DiscordNotificationService {
         eventId: event.id,
         contractAddress: contractConfig.address,
         fingerprint,
+        deduplication: this.deduplicator.getMetrics(),
       });
-      return false;
+      return true;
     }
     const logContext = {
       requestId,
@@ -82,6 +88,7 @@ export class DiscordNotificationService {
       logger.info('Discord notification delivered', {
         ...logContext,
         durationMs,
+        deduplication: this.deduplicator.getMetrics(),
       });
       return true;
     } catch (error) {
@@ -94,6 +101,10 @@ export class DiscordNotificationService {
     }
   }
 
+  getDeduplicationMetrics() {
+    return this.deduplicator.getMetrics();
+  }
+
   async sendTestMessage(requestId?: string): Promise<boolean> {
     const message: DiscordMessage = {
       embeds: [
@@ -235,3 +246,4 @@ export class DiscordNotificationService {
     }
   }
 }
+
diff --git a/listener/src/services/notification-deduplicator.test.ts b/listener/src/services/notification-deduplicator.test.ts
index 92fbae1..31a1fdd 100644
--- a/listener/src/services/notification-deduplicator.test.ts
+++ b/listener/src/services/notification-deduplicator.test.ts
@@ -100,6 +100,59 @@ describe('NotificationDeduplicator', () => {
     });
   });
 
+
+  describe('time window and metrics', () => {
+    it('allows the same fingerprint after the deduplication window expires', () => {
+      let now = 1000;
+      const d = new NotificationDeduplicator({ windowMs: 500, now: () => now });
+
+      d.markSent('CONTRACT:event-windowed');
+      expect(d.isDuplicate('CONTRACT:event-windowed')).toBe(true);
+
+      now = 1501;
+      expect(d.isDuplicate('CONTRACT:event-windowed')).toBe(false);
+      expect(d.size()).toBe(0);
+    });
+
+    it('reports skipped duplicate metrics accurately', () => {
+      const d = new NotificationDeduplicator({ windowMs: 1000 });
+
+      d.markSent('CONTRACT:event-1');
+      d.markSent('CONTRACT:event-2');
+      d.isDuplicate('CONTRACT:event-1');
+      d.isDuplicate('CONTRACT:event-1');
+      d.isDuplicate('CONTRACT:event-new');
+
+      expect(d.getMetrics()).toEqual({
+        acceptedRequests: 2,
+        skippedDuplicates: 2,
+        evictedEntries: 0,
+        expiredEntries: 0,
+        cacheSize: 2,
+        deduplicationWindowMs: 1000,
+      });
+    });
+
+    it('counts evicted and expired entries in metrics', () => {
+      let now = 0;
+      const d = new NotificationDeduplicator({ maxSize: 2, windowMs: 100, now: () => now });
+
+      d.markSent('fp-1');
+      d.markSent('fp-2');
+      d.markSent('fp-3');
+      now = 101;
+      d.size();
+
+      expect(d.getMetrics()).toEqual(
+        expect.objectContaining({
+          evictedEntries: 1,
+          expiredEntries: 2,
+          cacheSize: 0,
+        })
+      );
+    });
+  });
+
   describe('size', () => {
     it('returns 0 for a new deduplicator', () => {
       expect(new NotificationDeduplicator().size()).toBe(0);
@@ -140,3 +193,4 @@ describe('NotificationDeduplicator', () => {
     });
   });
 });
+
diff --git a/listener/src/services/notification-deduplicator.ts b/listener/src/services/notification-deduplicator.ts
index 141849b..8373d0b 100644
--- a/listener/src/services/notification-deduplicator.ts
+++ b/listener/src/services/notification-deduplicator.ts
@@ -1,37 +1,97 @@
 import logger from '../utils/logger';
 
 const DEFAULT_MAX_SIZE = 10000;
+const DEFAULT_WINDOW_MS = 60000;
 
 export function generateFingerprint(eventId: string, contractAddress: string): string {
   return `${contractAddress}:${eventId}`;
 }
 
+export interface NotificationDeduplicatorOptions {
+  maxSize?: number;
+  windowMs?: number;
+  now?: () => number;
+}
+
+export interface NotificationDeduplicationMetrics {
+  acceptedRequests: number;
+  skippedDuplicates: number;
+  evictedEntries: number;
+  expiredEntries: number;
+  cacheSize: number;
+  deduplicationWindowMs: number;
+}
+
 export class NotificationDeduplicator {
-  private readonly seen: Set<string>;
+  private readonly seen: Map<string, number>;
   private readonly maxSize: number;
+  private readonly windowMs: number;
+  private readonly now: () => number;
+  private acceptedRequests = 0;
+  private skippedDuplicates = 0;
+  private evictedEntries = 0;
+  private expiredEntries = 0;
 
-  constructor(maxSize = DEFAULT_MAX_SIZE) {
-    this.seen = new Set();
-    this.maxSize = maxSize;
+  constructor(options: NotificationDeduplicatorOptions | number = {}) {
+    const normalizedOptions = typeof options === 'number' ? { maxSize: options } : options;
+    this.seen = new Map();
+    this.maxSize = Math.max(1, normalizedOptions.maxSize ?? DEFAULT_MAX_SIZE);
+    this.windowMs = Math.max(1, normalizedOptions.windowMs ?? DEFAULT_WINDOW_MS);
+    this.now = normalizedOptions.now ?? Date.now;
   }
 
   isDuplicate(fingerprint: string): boolean {
-    return this.seen.has(fingerprint);
+    this.pruneExpired();
+    const expiresAt = this.seen.get(fingerprint);
+    const duplicate = expiresAt !== undefined && expiresAt > this.now();
+
+    if (duplicate) {
+      this.skippedDuplicates++;
+    }
+
+    return duplicate;
   }
 
   markSent(fingerprint: string): void {
+    this.pruneExpired();
     if (this.seen.size >= this.maxSize) {
-      const oldest = this.seen.values().next().value as string;
+      const oldest = this.seen.keys().next().value as string;
       this.seen.delete(oldest);
+      this.evictedEntries++;
       logger.warn('Notification deduplicator cache full, evicted oldest entry', {
         evicted: oldest,
         cacheSize: this.maxSize,
       });
     }
-    this.seen.add(fingerprint);
+    this.seen.set(fingerprint, this.now() + this.windowMs);
+    this.acceptedRequests++;
   }
 
   size(): number {
+    this.pruneExpired();
     return this.seen.size;
   }
+
+  getMetrics(): NotificationDeduplicationMetrics {
+    return {
+      acceptedRequests: this.acceptedRequests,
+      skippedDuplicates: this.skippedDuplicates,
+      evictedEntries: this.evictedEntries,
+      expiredEntries: this.expiredEntries,
+      cacheSize: this.size(),
+      deduplicationWindowMs: this.windowMs,
+    };
+  }
+
+  private pruneExpired(): void {
+    const now = this.now();
+    for (const [fingerprint, expiresAt] of this.seen) {
+      if (expiresAt > now) {
+        continue;
+      }
+
+      this.seen.delete(fingerprint);
+      this.expiredEntries++;
+    }
+  }
 }
diff --git a/listener/src/types/index.ts b/listener/src/types/index.ts
index 107ae76..027b6c7 100644
--- a/listener/src/types/index.ts
+++ b/listener/src/types/index.ts
@@ -6,6 +6,8 @@ export interface ContractConfig {
 export interface DiscordConfig {
   webhookUrl: string;
   webhookId: string;
+  deduplicationWindowMs?: number;
+  deduplicationMaxSize?: number;
 }
 
 export interface RetryQueueConfig {
@@ -25,3 +27,4 @@ export interface Config {
   discord?: DiscordConfig;
   retryQueue?: RetryQueueConfig;
 }
+