How would you set timeouts across an API request and its downstream dependencies?

Set timeout budgets across downstream dependencies

Sets bounded timeout and deadline policies across callers, APIs, databases, and external services without hiding unknown outcomes.

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I would start with the response-time objective for the whole user request, then give each dependency a smaller timeout inside that budget. The API must leave time to map the result and return it, so a downstream call cannot use the caller's entire deadline. I would configure the HTTP, database, or SDK timeout explicitly and pass cancellation through supported operations. A timeout means the result was not observed in time; it does not prove that a remote side effect did not happen.

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End-to-end deadlines, per-dependency timeouts, cancellation propagation, unknown outcomes, and latency-budget ownership.

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A timeout protects more than response time. It limits how long one dependency can hold request capacity, connections, and work that the caller may no longer need.
I would start with the response-time objective for the whole user request, then give each dependency a smaller timeout inside that budget. The API must leave time to map the result and return it, so a downstream call cannot use the caller's entire deadline. I would configure the HTTP, database, or SDK timeout explicitly and pass cancellation through supported operations. A timeout means the result was not observed in time; it does not prove that a remote side effect did not happen.
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For a request that calls several services, I would budget the critical path rather than assigning the same timeout everywhere. Sequential calls consume the budget one after another, while parallel calls share elapsed time but increase downstream concurrency. I would distinguish the caller disconnecting from my dependency deadline because they have different telemetry and recovery. Read calls may be abandoned safely, but a timed-out payment or write has an unknown outcome and needs an idempotency key, durable operation status, or reconciliation before any retry.

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Giving every dependency the full request timeout.
Treating a timeout as proof that no side effect occurred.
Configuring only the outer HTTP timeout.
Retrying before classifying the operation and outcome.
Logging caller cancellation and dependency timeout as the same event.

How would you set timeouts across an API request and its downstream dependencies?

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