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.
Deployment config mismatch: how to debug environment-specific config bugs
Your staging environment works. Production does not. The code is the same but the config is different — a missing setting, a wrong endpoint, or a different feature flag value.
Feature flag bug: how to debug unexpected feature flag behaviour
A feature flag is supposed to be off for some users but is on for everyone, or vice versa. The flag value, targeting rules, or flag evaluation is wrong.
Session cookie not working after deployment: how to debug it
Users were logged in. You deploy. Everyone is logged out. The session cookie is not being sent, not being recognised, or being set with wrong attributes after the new deployment.
Redirect URL wrong in production: how to debug redirect bugs
Your app redirects users to `http://localhost:3000/dashboard` in production. The redirect URL is hardcoded, or the origin detection is picking up the wrong value.
OAuth callback URL mismatch: how to debug OAuth redirect errors
OAuth login fails with 'redirect_uri_mismatch' after deployment. The callback URL in the request does not exactly match what is registered with the OAuth provider.
Database migration works locally but fails in production: how to debug it
Your migration runs perfectly on your local database but errors out in production. Different database version, different data, or different permissions.
Long-form thinking on debugging habits, observability, and the systems around the bug.
Tracking Down a 200 MB Leak with Python Memory Profilers
A production API was silently leaking 200 MB of RAM every hour. Here's how memory profilers found the culprit—a forgotten NumPy array reference—and how you can apply the same techniques.
Reading CPU Flame Graphs: What the Hot Colors Actually Tell You
Flame graphs are everywhere, but most engineers read them wrong. Here's how to identify real bottlenecks, avoid common misinterpretations, and turn profile data into actionable fixes.
When Logs Lie: The Gaps Between What You Log and What Actually Happened
Logs are the first thing we reach for during an incident. But they can be misleading, incomplete, or outright wrong. Here's when to trust them and when not to.
Adding Observability to a 500K-Line Monolith Without a Rewrite
Adding structured logging, distributed tracing, and metrics to a legacy monolith without a full rewrite. Real code examples and a war story from a 500K-line codebase.
Distributed Tracing: Following a Single Request Across Microservices
Distributed tracing lets you follow a request as it hops across services. I'll show you how trace context propagates, why sampling matters, and how tracing helped us debug a 5-second latency spike in production.
Structured Logging in JSON: Fields, Schemas, and Pitfalls from Production
A practical guide to designing JSON log schemas that are queryable, consistent, and actually useful in production — with field recommendations and a war story.