DEVELOPER GUIDEHow to prevent duplicate WhatsApp messages
Use idempotency keys and durable event records so retries never become duplicate customer alerts.
Developer guide for duplicate messages. Validate the behavior in your own stack before production rollout.The problem
Derive one key from the source event revision and recipient before the first send.
Most duplicates are a lost response followed by a retry that looks like a new send.Design the boundary
Send the same key on every retry and store the resulting message ID against the source event.
Derive the key from the event revision and recipient, not from a random value per attempt.Process the interaction
Treat timeouts as unknown outcomes; retry with the original key and cap attempts.
One alert keeps the conversation about the order, not about the duplicate.Measure the outcome
Measure duplicate conflicts, retry count and dead-lettered sends.
BUILD IT SAFELYMake the failure path part of the design.
Reliable messaging is an operational system, not only an API call.
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