A downstream service is slow and your API starts timing out. How would you respond?

Triage downstream dependency latency

Explains how to diagnose and mitigate a downstream dependency slowing the API through timeouts, retries, and degraded behavior.

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I would confirm which dependency is slow, which endpoints call it, and whether the API is failing because of timeout, retry storm, connection exhaustion, or thread pressure. Then I would reduce user impact: lower concurrency to that dependency, disable noncritical calls, use cached or degraded responses where safe, or return a clear temporary error instead of tying up all API resources. The first goal is to stop one dependency from consuming the whole API.

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Dependency latency, timeouts, retries, circuit breakers, fallback, user impact, and provider communication.

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Dependency incidents punish APIs that wait too long, retry too hard, or fail without a user-facing fallback.
I would confirm which dependency is slow, which endpoints call it, and whether the API is failing because of timeout, retry storm, connection exhaustion, or thread pressure. Then I would reduce user impact: lower concurrency to that dependency, disable noncritical calls, use cached or degraded responses where safe, or return a clear temporary error instead of tying up all API resources. The first goal is to stop one dependency from consuming the whole API.
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I would inspect dependency duration, timeout rate, retry count, circuit-breaker state, request volume, and downstream status pages or logs. Retries need backoff and limits; otherwise the API can make the dependency incident worse. Timeouts should be shorter than the caller's timeout budget. If the dependency is optional, the API should degrade. If it is critical, the API should fail quickly and honestly.

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Retrying every timeout aggressively.
Using dependency timeouts longer than the user-facing request timeout.
No degraded behavior for optional dependencies.
Letting one dependency consume all API concurrency.

A downstream service is slow and your API starts timing out. How would you respond?

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