Hi @syedaayesha15!
To prevent duplicates, treat Zoom webhooks as “at-least-once” delivery and make your handler idempotent: persist a dedupe key and no-op if you’ve already processed it. In practice, you can key off the request’s X-Zm-Trackingid (unique per delivery) plus your own business key (meeting UUID + participant ID) and store the first-seen timestamp.
For retries, Zoom will retry failed deliveries and considers any 2xx response as successfully delivered (their docs also describe the retry attempt timing). The reliable pattern is to ACK fast (return 2xx once you’ve safely queued/persisted the event), then process asynchronously; also verify authenticity using the x-zm-signature / secret token validation flow.
Regarding Server-toServer apps: yes, JWT is deprecated and Zoom recommends migrating backend integrations to Server-to-Server OAuth.