Buglyst Blog
Learn to debug under pressure.
Playbooks for fast pattern recognition, guides for the full investigation, and articles for the engineering judgment around the edges.
17 playbooks · 509 guides · 95 articles · 12 linked practice labs ·skip to practice
Fast pattern recognition for the production failures engineers see most often.
1 playbook in Languages & Runtime
Structured investigations for the failure modes engineers meet in real systems.
Case-sensitive import fails on Linux: how to debug it
Your import works on macOS and Windows but fails on Linux with 'module not found'. The fix is a single character.
Timezone off by one day in JavaScript: how to debug it
Your date shows the wrong day because of a timezone offset. The date string, parser, or display format is silently shifting it.
Worker process memory leak: how to find and fix memory leaks in background jobs
Your background worker's memory usage grows steadily until it crashes. The leak is accumulating across jobs — each job leaves something behind.
Request body undefined in Express: how to debug missing request bodies
Your Express route handler receives `req.body` as `undefined` or an empty object. The body parser is missing, misconfigured, or not matching the content type.
ESM CommonJS import error: how to debug module system conflicts
Your import breaks with 'require is not defined' or 'Cannot use import outside a module'. The file is being treated as the wrong module system.
Tracking Down Node.js Memory Leaks in Production
Diagnosing and fixing Node.js memory leaks in real production systems, with step-by-step commands, signals, and non-obvious debugging tactics.
Long-form thinking on debugging habits, observability, and the systems around the bug.