Backend Debugging Tasks

Introduction

Debugging is the highest-leverage skill in backend engineering. Practise these scenarios.

Understanding the topic

• Mystery 500 — given logs + a stack trace, find the bug.
• Slow endpoint — p95 doubled overnight; identify with traces, fix root cause.
• N+1 in production — diagnose with Hibernate stats, fix without breaking pagination.
• Phantom data — a row appears that shouldn't; trace through events + outbox.
• Memory leak — heap grows; capture a heap dump, find the retainer.