Webhook flow

Webhook detection is wired in WebhookController. The dispatcher routes to per-platform processors. Instagram is currently a no-op which makes adding it straightforward.

The core pattern is accept-fast, process-durably: Meta gets a 200 before any business logic runs. Retries are owned by the worker, not Meta.

Where to start

Open webhook.controller.ts. Three routes worth knowing:

• GET /webhook — Meta verification handshake using hub.verify_token
• POST /webhook — classifies body.object and hands off to the repo
• webhook-event.dispatcher.ts — routes by platform

Storage is a single events collection keyed by SHA-256(body), which gives idempotency for free when Meta retries the same payload.

Gotchas

The in-memory processingMessages Set is per-process. If you horizontally scale, two pods may double-handle the same message ID within the same DB tick. The DB-level platformMessageId unique index is the actual idempotency guard, not the in-memory Set.