Interview › Databases & Caching
What is Performance Insights, and what does it help you find?
Databases & Caching · Basic level
Answer
RDS performance monitoring should combine CloudWatch, Performance Insights, Enhanced Monitoring, database-native views, logs, and application SLOs. CloudWatch shows resource symptoms; Performance Insights shows database load, waits, and top SQL; the app tells whether users are impacted.
Technical explanation
Key metrics include CPU, connections, free memory, free storage, IOPS, read/write latency, disk queue depth, replica lag, and DB load.
High CPU is investigated through top SQL, waits, connection count, recent deployments, locks, and query plans.
The best incident response correlates application latency with database load and the exact SQL or wait event causing it.
Hands-on example
Incident triage SQL:
SELECT state, wait_event_type, wait_event, count(*) FROM pg_stat_activity GROUP BY 1,2,3 ORDER BY count(*) DESC;
Then open Performance Insights, identify top SQL by DB load, run EXPLAIN (ANALYZE, BUFFERS) in staging, and mitigate with query change, index, pool cap, feature flag, or scale-up.
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