Webhook
An event notification sent as an HTTP request to an endpoint you configure, so your application can react without repeatedly polling.
Key points
- 01 A webhook delivers an event notification to a configured HTTP endpoint instead of requiring constant polling.
- 02 Providers commonly send a POST request with an event payload; consult the provider’s contract for the actual method, format and acknowledgement behavior.
- 03 Respond promptly according to that contract. Stripe, for example, recommends a successful 2xx response before complex business logic that could time out.
- 04 A delivery can be retried or repeated. Track an appropriate event or business identifier so repeating delivery does not repeat an unintended effect.
- 05 Delivery order is not universally guaranteed; Stripe explicitly warns against relying on events arriving in generation order.
- 06 Verify authenticity using the provider’s documented mechanism. Stripe signatures require the original request body, signature header and endpoint signing secret.
- 07 A notification can arrive later than the event and may arrive more than once. Receipt is not proof that all downstream work has finished.
Follow the reviewed diagram below. A separate worked example is not available for this lesson yet.
Visual
sequenceDiagram participant S as Event source participant R as Your endpoint participant W as Application work Note over S,R: Endpoint is configured in advance S->>R: Deliver event notification Note over R: Verify and accept using provider contract R-->>S: Prompt acknowledgement R->>W: Continue accepted work S->>R: Possible repeated delivery Note over R: Avoid repeating the same effect
Follow the primary sources
- Stripe Docs: Receive Stripe events in your webhook endpoint
Primary documentation supporting this written explanation.
Written explanation: sources and review
The summary, key points and diagram were independently compared with primary documentation using AI on 2026-10-07. The approval is bound to this written content.
This text review does not approve a video or timestamp window. Human learner validation remains pending.
Practice · predict the result
Count events, not deliveries
A small test from your robot instructors. Hints are welcome.
What you will practice: Identify a repeated webhook event and predict the effect of deduplicating by its event ID.
Sample scenario. Synthetic receiver, starting at zero with no processed IDs. Every delivery is authentic. Recording an ID and incrementing the counter commit together; no crashes occur. Distinct IDs represent distinct operations in this example.
- Starting counter
0- Already processed IDs
None- Delivery 1
evt-alpha — First delivery of event alpha- Delivery 2
evt-alpha — Retry of event alpha after a lost acknowledgment- Delivery 3
evt-beta — First delivery of event beta
This receiver increments a counter once per event ID. After these three deliveries, what is the counter?
Attempts stay on this browser and are kept separate from lesson views and your self-reported knowledge.
Sources and exercise scope
- Stripe: Handle duplicate webhook events
Repeated event deliveries can be identified by event ID; separate event objects may also describe a duplicate business event.
Original synthetic exercise, checked with AI against primary documentation on 2026-10-07. Human learner validation is pending. A result here records this attempt; it does not establish mastery.
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