In a monolith, a bug lives in one place. You open the logs, you find it.

Microservices change the problem. A single user action can cross 5+ services — and the failure can sit in any one of them, or in the gap between two of them.

Take a signup:

Auth service → User service → Notification service → Email provider

Say it fails halfway. The user exists, but the welcome never arrives. Or the account never gets created, but the notification already went out. Where do you look?

Without centralised logging and tracing, you open four dashboards, four log files, four different formats — and you guess. Each team can honestly say "it worked on my side," because each side only saw its own hop.

The fix is not more logs.…