Callback Response

Overview

Meaning and scope

Callback Response is the HTTP or protocol result returned by a callback receiver to acknowledge, reject, or describe handling of a delivery attempt. It is used to tell the sender whether delivery was accepted and whether retry behavior should continue. It differs from the internal processing result, which may complete after an immediate acknowledgment.

Mechanism and operation

The handler validates enough information to decide its response, returns the documented status and body within the deadline, and processes durable work according to its design. A receiver should treat transport acknowledgement and successful downstream processing as separate states for Callback Response. A Callback Response handler should acknowledge only after durable receipt when the provider’s retry contract depends on the response. Operational evidence should include event ID, response status and body, latency, durable receipt ID, retry decision, and later processing outcome. Callback Response should be documented alongside Webhook Timeout, Callback Handler, and Callback Retry.

Practical payment example

The merchant callback receiver returns an acknowledgment quickly, then processes payment records asynchronously to avoid repeated webhook deliveries.

Operational checks

Business actions triggered by Callback Response should be idempotent and should verify the current object state before fulfillment or accounting updates. Monitoring for Callback Response should track delivery age, signature failures, duplicate rate, retry exhaustion, and unresolved business events.

Distinctions and limits

Replay of Callback Response should preserve original identifiers and timestamps so historical processing cannot masquerade as a new event. Common risks include returning success before durable receipt can lose events and while slow or inconsistent responses can cause repeated deliveries and overload.

Related reading

Related definitions: Webhook Timeout, Callback Handler.