What should I check for slow APIs, memory growth or intermittent 500s?

Definition:

Slow responses, growing memory and 500 errors are symptoms, not root causes. A useful investigation connects each symptom to a specific route, instance, input or dependency. Comparing healthy and unhealthy requests often narrows the problem faster than changing settings blindly.

Key points:

• Slow API: separate app time, pool wait, DB time and external API time.

• Memory growth: compare heap snapshots; inspect caches, listeners and large payloads.

• 500s: group errors by route, app instance and deployment; use request IDs to trace failures.

• Check release timing and resource saturation, but keep multiple hypotheses until measurements distinguish them.

Interview point:

• State what evidence would confirm or reject your first hypothesis, then verify the fix with the same measurement.