Performance / Scenario
Fast Query, Slow Page
The database query is 15ms and the DB is 20% busy, yet p95 is 3 seconds. Find where the requests are really waiting.
- Difficulty
- Hard
- Format
- Scenario
- Points
- 200
- Estimate
- 15 min
// MISSION BRIEF
Your Mission
A service crawls under load. The database query is 15ms. DB CPU is 20%. And yet page p95 is 3 seconds. The requests are waiting somewhere, and it is not the database doing work.
Read the metrics and the pool config, find the real bottleneck, and avoid the tempting fix that just moves it.
// FIRST CONTACT
Battle teaser
First artifact
Metrics during the slowdown
Why is p95 3s when the query is 15ms and DB CPU is 20%?
- AThe connection pool (size 10) is saturated; requests queue waiting for a free connection, so wait time, not query time, dominates
- BThe network to the database is congested
- CThe app servers are out of CPU
- DThe database is slow
Answers, scoring, hints, and the full battle stay sealed.
// SKILL TAGS
performanceconnection-poolsaturationdatabase