How do I identify the slow part of an API?
Understand the concept
API latency is the total time a request spends waiting and doing work across the system. That time can include load-balancer delay, connection-pool wait, application CPU, database work and external calls. Breaking it into stages turns “the API is slow” into a testable explanation.
Important ideas
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Measure request time, database time, external calls and queue/pool waits separately.
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Check p95/p99 latency too; averages can hide slow requests.
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Compare the same traffic and workload before and after a fix.
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Distinguish throughput from latency: many completed requests per second can coexist with a badly delayed minority of requests.
Can you explain it without the notes?
How do I identify the slow part of an API?
Use your own words. Explain an example and one limitation before checking the explanation.
Check your explanation
API latency is the total time a request spends waiting and doing work across the system. That time can include load-balancer delay, connection-pool wait, application CPU, database work and external calls. Breaking it into stages turns “the API is slow” into a testable explanation.
Turn this concept into a clear answer.
- Use percentiles and traces to find the affected users and slow stage rather than relying only on average response time.
Keep connecting the ideas.
Next lesson: When should I use pagination, streaming, compression or a CDN?Adapted from 08_PERFORMANCE_SECURITY.md · “How do I identify the slow part of an API?”. Examples are study fragments; framework behavior can depend on your version.