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.
17 playbooks
Debugging Env Var Issues
A concise checklist for incidents where local works but CI, staging, or production changes behavior.
Debugging Cache Stampedes
How to recognize and contain request spikes when cached data expires.
Debugging CORS Origin Bugs
A practical way to inspect origin parsing, credentials, and header behavior.
Debugging Retry Bugs
Retry issues often hide the first failure and create duplicate work.
Debugging Timezone Bugs
Time bugs usually live at day boundaries, DST changes, and unit conversions.
Debugging Pagination Bugs
Pagination bugs hide in boundary math, cursor reuse, and new records arriving between pages.
Structured investigations for the failure modes engineers meet in real systems.
Cron job not running in production: how to debug scheduled tasks
Your cron job runs fine when triggered manually but never fires on its schedule in production. The scheduler, timezone, or environment is wrong.
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.
Rate limit bug: how to debug unexpected rate limiting issues
Legitimate users are hitting rate limits. The limiter is too aggressive, counting wrong, or sharing state across instances when it should not.
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.
GitHub Actions missing secret: how to debug CI secret issues
Your GitHub Actions workflow references a secret that does not exist in the repository settings. The workflow fails with an empty value or an error.
Long-form thinking on debugging habits, observability, and the systems around the bug.
The Art of the Minimal Reproducible Example: A Debugging Superpower
A minimal reproducible example (MRE) is more than just a snippet — it's a tool that isolates the bug, saves time, and gets you faster answers. Here's how to build one that works, with a real-world war story.
Retry Storms: When Retries Make a Cascading Failure Worse
Retries seem like a safety net, but in a distributed system under load they can turn a small hiccup into a full outage. Here's how retry storms form and what to do about them.
Caching Bugs Are the Worst: A Postmortem on Stale Data Disasters
A deep dive into the most insidious caching bugs, with real postmortems and practical patterns to avoid stale-data disasters.
Observability vs. Monitoring: Why Your On-Call Rotation Still Wakes You Up at 3 AM
Monitoring tells you something is broken. Observability lets you figure out why—without guessing, without SSH, without restarting the pod.
Debugging Flaky Tests for Good: A Systematic Approach to Root Cause Analysis
Flaky tests waste time and erode trust. Here's how to find and fix the actual root cause instead of just rerunning.
Idempotency Keys: The Safety Net Your Payment API Needs
How idempotency keys prevent double charges, lost refunds, and data corruption in payment APIs. With real-world examples and edge cases you haven't considered.