diff --git a/src/modules/indexer/event-dedup-guard.unit.test.ts b/src/modules/indexer/event-dedup-guard.unit.test.ts
new file mode 100644
index 0000000..9c77796
--- /dev/null
+++ b/src/modules/indexer/event-dedup-guard.unit.test.ts
@@ -0,0 +1,263 @@
+import { processIndexerChainEvents, IndexerChainEvent } from '../../utils/indexer-event-processor.utils';
+
+jest.mock('../../utils/logger.utils', () => ({
+   logger: { info: jest.fn(), debug: jest.fn(), warn: jest.fn() },
+}));
+
+function makeEvent(overrides: Partial<IndexerChainEvent> = {}): IndexerChainEvent {
+   return {
+      txHash: '0xabcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890',
+      eventIndex: 0,
+      eventType: 'KEY_BOUGHT',
+      ledger: 1000,
+      ...overrides,
+   };
+}
+
+describe('event deduplication guard — (txHash, eventIndex) composite key', () => {
+   describe('new event pair is processed', () => {
+      it('calls the handler exactly once for a new (txHash, eventIndex) pair', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const event = makeEvent({ txHash: '0xaaa', eventIndex: 0 });
+
+         await processIndexerChainEvents([event], handler);
+
+         expect(handler).toHaveBeenCalledTimes(1);
+         expect(handler).toHaveBeenCalledWith(event);
+      });
+
+      it('inserts the event into the DB on first appearance', async () => {
+         const db: { records: IndexerChainEvent[] } = { records: [] };
+
+         const handler = jest.fn().mockImplementation(async (e: IndexerChainEvent) => {
+            db.records.push(e);
+         });
+
+         await processIndexerChainEvents([makeEvent({ txHash: '0xbbb', eventIndex: 1 })], handler);
+
+         expect(db.records).toHaveLength(1);
+         expect(db.records[0].txHash).toBe('0xbbb');
+         expect(db.records[0].eventIndex).toBe(1);
+      });
+   });
+
+   describe('duplicate pair is skipped', () => {
+      it('does not call the handler for a duplicate (txHash, eventIndex) in the same batch', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xccc', eventIndex: 0 }),
+            makeEvent({ txHash: '0xccc', eventIndex: 0 }), // exact duplicate
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         // Guard skips the duplicate — handler called only once
+         expect(handler).toHaveBeenCalledTimes(1);
+      });
+
+      it('keeps DB event count at 1 after processing a duplicate pair', async () => {
+         const db: { records: IndexerChainEvent[] } = { records: [] };
+         const handler = jest.fn().mockImplementation(async (e: IndexerChainEvent) => {
+            db.records.push(e);
+         });
+
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xddd', eventIndex: 2 }),
+            makeEvent({ txHash: '0xddd', eventIndex: 2 }), // duplicate
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(db.records).toHaveLength(1);
+      });
+
+      it('skips all extra copies when the same event appears three times', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xeee', eventIndex: 5 }),
+            makeEvent({ txHash: '0xeee', eventIndex: 5 }),
+            makeEvent({ txHash: '0xeee', eventIndex: 5 }),
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(1);
+      });
+
+      it('does not trigger side effects (balance update, price snapshot) on a skipped event', async () => {
+         const balanceUpdate = jest.fn();
+         const priceSnapshot = jest.fn();
+
+         const handler = jest.fn().mockImplementation(async () => {
+            balanceUpdate();
+            priceSnapshot();
+         });
+
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xfff', eventIndex: 0 }),
+            makeEvent({ txHash: '0xfff', eventIndex: 0 }), // duplicate — side effects must NOT fire again
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(balanceUpdate).toHaveBeenCalledTimes(1);
+         expect(priceSnapshot).toHaveBeenCalledTimes(1);
+      });
+   });
+
+   describe('same txHash, different eventIndex are distinct events', () => {
+      it('processes both events when txHash is the same but eventIndex differs', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0x111', eventIndex: 0 }),
+            makeEvent({ txHash: '0x111', eventIndex: 1 }), // different index → new event
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(2);
+         expect(handler).toHaveBeenNthCalledWith(1, expect.objectContaining({ txHash: '0x111', eventIndex: 0 }));
+         expect(handler).toHaveBeenNthCalledWith(2, expect.objectContaining({ txHash: '0x111', eventIndex: 1 }));
+      });
+
+      it('writes two DB records for same txHash with eventIndex 0 and 1', async () => {
+         const db: { records: IndexerChainEvent[] } = { records: [] };
+         const handler = jest.fn().mockImplementation(async (e: IndexerChainEvent) => {
+            db.records.push(e);
+         });
+
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0x222', eventIndex: 0 }),
+            makeEvent({ txHash: '0x222', eventIndex: 1 }),
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(db.records).toHaveLength(2);
+         const indices = db.records.map(r => r.eventIndex).sort();
+         expect(indices).toEqual([0, 1]);
+      });
+
+      it('treats events with different txHash but same eventIndex as distinct', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xaaa', eventIndex: 3 }),
+            makeEvent({ txHash: '0xbbb', eventIndex: 3 }), // different hash, same index
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(2);
+      });
+   });
+
+   describe('mixed batches with unique and duplicate events', () => {
+      it('processes only unique events from a batch containing both', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: 'tx1', eventIndex: 0 }),
+            makeEvent({ txHash: 'tx2', eventIndex: 0 }),
+            makeEvent({ txHash: 'tx1', eventIndex: 0 }), // duplicate of first
+            makeEvent({ txHash: 'tx3', eventIndex: 0 }),
+            makeEvent({ txHash: 'tx2', eventIndex: 0 }), // duplicate of second
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(3);
+      });
+
+      it('preserves first-occurrence order when deduplicating a batch', async () => {
+         const processed: string[] = [];
+         const handler = jest.fn().mockImplementation(async (e: IndexerChainEvent) => {
+            processed.push(`${e.txHash}:${e.eventIndex}`);
+         });
+
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: 'txZ', eventIndex: 0 }),
+            makeEvent({ txHash: 'txA', eventIndex: 0 }),
+            makeEvent({ txHash: 'txZ', eventIndex: 0 }), // duplicate
+            makeEvent({ txHash: 'txM', eventIndex: 0 }),
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(processed).toEqual(['txZ:0', 'txA:0', 'txM:0']);
+      });
+
+      it('DB count equals the number of unique (txHash, eventIndex) pairs in the batch', async () => {
+         const db: { records: IndexerChainEvent[] } = { records: [] };
+         const handler = jest.fn().mockImplementation(async (e: IndexerChainEvent) => {
+            db.records.push(e);
+         });
+
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: 'ta', eventIndex: 0 }),
+            makeEvent({ txHash: 'ta', eventIndex: 1 }),
+            makeEvent({ txHash: 'tb', eventIndex: 0 }),
+            makeEvent({ txHash: 'ta', eventIndex: 0 }), // duplicate
+            makeEvent({ txHash: 'tb', eventIndex: 0 }), // duplicate
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         // 5 events in → 3 unique pairs (ta:0, ta:1, tb:0) → 3 DB records
+         expect(db.records).toHaveLength(3);
+      });
+   });
+
+   describe('edge cases', () => {
+      it('processes an empty batch without errors', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+
+         await expect(processIndexerChainEvents([], handler)).resolves.not.toThrow();
+         expect(handler).not.toHaveBeenCalled();
+      });
+
+      it('processes a single-event batch correctly', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const event = makeEvent({ txHash: '0xsingle', eventIndex: 0 });
+
+         await processIndexerChainEvents([event], handler);
+
+         expect(handler).toHaveBeenCalledTimes(1);
+         expect(handler).toHaveBeenCalledWith(event);
+      });
+
+      it('deduplication key is case-sensitive for txHash', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xABC', eventIndex: 0 }),
+            makeEvent({ txHash: '0xabc', eventIndex: 0 }), // different case → treated as different
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(2);
+      });
+
+      it('handles eventIndex 0 correctly — does not confuse falsy value with missing key', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xzero', eventIndex: 0 }),
+            makeEvent({ txHash: '0xzero', eventIndex: 0 }), // duplicate with index 0
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(1);
+      });
+
+      it('handles large eventIndex values without collision', async () => {
+         const handler = jest.fn().mockResolvedValue(undefined);
+         const events: IndexerChainEvent[] = [
+            makeEvent({ txHash: '0xlarge', eventIndex: 999999999 }),
+            makeEvent({ txHash: '0xlarge', eventIndex: 999999999 }), // duplicate
+         ];
+
+         await processIndexerChainEvents(events, handler);
+
+         expect(handler).toHaveBeenCalledTimes(1);
+      });
+   });
+});