Understanding what is happening.
WHY IT IS HARDER
One user action touches several services, and no single log contains the whole story.
WHAT TO IMPLEMENT
Structured logging A correlation identifier propagated through every call Distributed tracing Metrics per service Health endpoints
WHAT THE CORRELATION IDENTIFIER DOES
Ties every log entry across every service to one originating request.
WHY THAT IS ESSENTIAL
Without it, diagnosing a distributed failure is guesswork.
WHAT TRACING PROVIDES
A view of one request across services, showing where time was spent.
WHAT METRICS TO COLLECT
Request rate Error rate Latency, including the slow end rather than only averages Saturation of resources
WHY THE SLOW END
Averages conceal the experience of the worst-affected users.
WHAT TO CENTRALISE
Logs, so they can be searched together.
WHAT TO ALERT ON
Error rate Latency degradation A service failing health checks
WHAT TO TEST
That you can trace a single request end to end.
