Add Transaction Duplicate Detection

[llinsss]

Description:
Detect and prevent duplicate transaction submissions.

Tasks:

• Implement transaction fingerprinting
• Check for duplicates before processing
• Add duplicate detection window
• Return existing transaction if duplicate

Files to modify:

• backend/services/PaymentService.js

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[rosemary21]

@rosemary21 has applied to work on this issue as part of the Stellar Wave Program's 2nd wave.

I’m very interested in implementing duplicate transaction detection because idempotency and transaction integrity are critical in any payment system. Preventing duplicate submissions protects users from being charged multiple times, improves system reliability, and reduces reconciliation issues. This feature directly enhances trust in the platform’s financial operations.

Relevant Experience

Payment Systems & Idempotency

Implemented idempotency keys and transaction fingerprinting in payment APIs.

Designed duplicate detection logic using hashed payloads and time-based windows.

Returned previously processed transactions for safe retry scenarios.

Concurrency & Race Condition Handling

Managed concurrent requests using database constraints and atomic operations.

Prevented double processing through locking mechanisms and unique indexes.

Designed safe retry mechanisms for network timeouts and client resubmissions.

Backend Service Architecture

Worked extensively in Node.js service layers similar to PaymentService.js.

Implemented validation and pre-processing checks before executing financial operations.

Structured services to separate validation, fingerprinting, processing, and persistence layers

ℹ️ Repo Maintainers: To accept this application, review their application or assign @rosemary21 to this issue.

[obed-smart]

@obed-smart has applied to work on this issue as part of the Stellar Wave Program's 2nd wave.

Hi 👋 I’d love to work on this issue.
I have experience with JavaScript, backend development, and I’m comfortable following contribution guidelines.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @obed-smart to this issue.

[drips-wave]

Congratulations, @rosemary21! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on February 26, 2026.

🧑‍💻 @rosemary21: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[drips-wave]

This issue has been completed by @rosemary21 as part of the Stellar Wave Program's 2nd Wave 🥳

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