Chapter 3

Finding the Bottleneck

When the test fails, where do you look?

~23 min total3 lessonsAssignment

By the end of this chapter you'll be able to

Use Pulse + DB metrics + system stats to localise the problem
Distinguish API CPU, DB CPU, network, and test-rig limits

Lessons

Module: Diagnosis

Reading the numbers

p50 vs p95 vs p99 — what each tells you.

7mmedium

Common bottlenecks

DB connection pool, N+1, cold caches, GC pauses.

9mmedium

Fix and prove it

Make a change, re-run, compare — disciplined performance work.

7mmedium

Chapter assignment

Find + fix + prove

Pick the endpoint with the worst p95 from your suite. Use Pulse + DB logs to identify the bottleneck. Fix it (add an index, add caching, fix N+1). Re-run the same scenario. Paste before/after numbers in notes.md with a 1-paragraph writeup.

See success criteria

Lesson 1 takes ~7 min.

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ch.2: The Five Test Types ch.4: k6 in CI