Users complain about slow system performance. The frontend communicates with the backend through an API Gateway, and the backend works with PostgreSQL and Redis. How would you investigate the cause of the performance degradation?

To identify the cause of performance degradation in a system with Frontend → API Gateway → Backend → PostgreSQL and Redis, you can proceed step-by-step:

1. Metrics and logs collection

   • Check load metrics on Frontend, API Gateway, Backend.
   • Study error and warning logs.

2. Response time analysis at each level

   • Measure API Gateway response time.
   • Check Backend request processing time.
   • Evaluate query execution times for PostgreSQL and Redis.

3. Bottleneck identification

   • In Backend: code profiling, identifying long operations.
   • In PostgreSQL: analyze slow queries (slow query log), indexes, locks.
   • In Redis: check load, delays, possible network issues.

4. Infrastructure check

   • Server load, CPU, memory, disk usage.
   • Network delays between components.

5. Testing and reproducing the issue

   • Try to reproduce slowdown under load.
   • Use distributed tracing tools.

6. Optimization

   • Caching frequently requested data.
   • Query optimization.
   • Scaling components if necessary.

Thus, a systematic approach with monitoring, profiling, and analysis will help identify and eliminate the cause of slowdown.