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Performance Troubleshooting

Diagnose and fix performance issues.

Slow API Responses​

Database Queries​

Symptom: Endpoints take > 1 second

Diagnosis:

-- Find slow queries in PostgreSQL
SELECT pid, now() - pg_stat_activity.query_start AS duration, query
FROM pg_stat_activity
WHERE state = 'active'
ORDER BY duration DESC;

Fixes:

  1. Add database indexes for frequently queried columns
  2. Reduce relations in API queries
  3. Use pagination (page + limit params)
  4. Enable query caching with Redis

N+1 Query Problem​

Symptom: Many small queries instead of one JOIN

Fix: Use eager loading for relations:

const result = await this.service.findAll({
  relations: ["user", "organization"],
});

High Memory Usage​

Symptom: API process exceeding memory limits

Fixes:

  1. Increase NODE_OPTIONS="--max-old-space-size=4096"
  2. Check for memory leaks (unclosed connections, large caches)
  3. Use streaming for large data exports

Redis Performance​

Diagnosis:

redis-cli INFO memory
redis-cli INFO stats
redis-cli SLOWLOG GET 10

Fixes:

  1. Set appropriate maxmemory and eviction policy
  2. Monitor key expiration
  3. Use Redis Cluster for large datasets

Frontend Performance​

Fixes:

  1. Enable lazy loading for feature modules
  2. Use OnPush change detection strategy
  3. Implement virtual scrolling for long lists
  4. Optimize images and assets