feat: Resilient Webhook Ingestion System for Frontend External Triggers

[ACodehunter]

Closes #223

Summary

Builds a highly resilient, decoupled webhook ingestion pipeline that survives database outages by using a Redis-based message queue with a dedicated worker, exponential backoff retries, and a Dead Letter Queue.

Changes

New Files

• backend/src/routes/webhooks.ts — Fast-ingest endpoint (POST /api/v1/webhooks/ingest). Verifies signature and immediately enqueues; returns 200 OK within milliseconds.
• backend/src/services/queue.service.ts — Redis list-backed queue: enqueueWebhook, dequeueWebhook, and enqueueDLQ.
• backend/src/services/webhookWorker.ts — Standalone worker process that consumes the queue, processes business logic, and retries with exponential backoff before moving to DLQ.
• backend/src/utils/signature.ts — HMAC-SHA256 signature verification using crypto.timingSafeEqual to prevent timing attacks.
• backend/src/utils/redis.ts — Shared Redis client.

Modified Files

• backend/src/routes/index.ts — Registered webhook router at /webhooks.
• backend/.env.example — Added WEBHOOK_SECRET and REDIS_URL.

Implementation Details

Phase 1 — Fast-Ingest Endpoint

POST /api/v1/webhooks/ingest verifies the X-Webhook-Signature header and pushes the payload onto a Redis list immediately, returning 200 { status: 'accepted' } without any business logic.

Phase 2 — Worker Service

webhookWorker.ts runs as a separate process via BLPOP on the Redis queue (blocking pop, zero-overhead). Processes each webhook with the actual business logic.

Phase 3 — Cryptographic Signature Verification

HMAC-SHA256 signature is verified using crypto.timingSafeEqual preventing timing-based spoofing attacks. Unsigned requests are immediately rejected with 401.

Phase 4 — Dead Letter Queue + Exponential Backoff

• Max 5 retries with delay calculated as 2^attempt * 1000ms.
• After max retries, payload is moved to webhooks:dlq Redis list for manual inspection and replay.

[ACodehunter]

Closing — opened from incorrect account. Will be re-opened from the correct account.

[ayomideadeniran]

pr under review, if i find any wrong implementation i will notify you.