AI & Technical question

Design a webhook.

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What this question tests

Tests technical fundamentals of asynchronous system integration: delivery guarantees, retries, and security.

Clarify the use case: what event triggers the webhook and what the receiver needs to do with it.
Define the contract: an HTTP POST with a JSON payload schema, an event type, and a unique event ID.
Address reliability: retries with exponential backoff on failure, expecting a 2xx acknowledgment.
Address idempotency: since retries can duplicate delivery, require the event ID so receivers can ignore repeats.
Address security: sign each payload so the receiver can verify it actually came from your service.
Define quality measurement: delivery success rate and average retry count, since high retries signal an unreliable endpoint.

Explicitly handles retries and idempotency together, the core hard problem in webhook design.
Adds payload signing for security, a standard expected practice for real webhook systems.
Picks delivery success rate as the concrete quality metric tied to what matters operationally.

Designing only the happy-path single delivery with no retry or failure handling.
No security consideration for payload signing or verification.

How would you handle a receiving endpoint that's down for an extended period?
How would you let developers test their integration safely?
How would you version the payload schema without breaking existing integrations?