Vonage Verify callbacks: acknowledge durable acceptance and handle retries safely

Verify the signed Vonage Verify callback, durably accept it, then return 200 or 204. Vonage documents retries after a non-2xx response. Run slow processing after durable acceptance so acknowledging a callback does not lose work.

Make repeated delivery of the same notification safe. Do not discard every later callback with the same request_id: one verification can produce event and summary callbacks carrying different state. Track the notification or state transition as well as the request, and make each side effect idempotent. Test both a repeated callback and distinct progress/completion callbacks for one request.

Vonage’s official guide documents signed callbacks, 200/204 acknowledgements, non-2xx retries, and event/summary payloads with a shared request_id. Durable acceptance and per-notification idempotence are engineering recommendations inferred from those semantics; the guide does not promise exactly-once delivery or define a universal deduplication key. Source: https://developer.vonage.com/en/verify/concepts/webhooks