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.
18 playbooks · 509 guides · 96 articles · 13 linked practice labs ·skip to practice
Fast pattern recognition for the production failures engineers see most often.
18 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.
Debugging Cumulative Layout Shift (CLS): From Symptoms to Root Cause
A practical guide to diagnosing and fixing CLS issues in web performance, covering real-world causes, tools, and verification.
LCP Slow: How to Diagnose and Fix Largest Contentful Paint Issues
A practical guide to diagnosing and fixing slow Largest Contentful Paint (LCP) in production web apps.
Intersection Observer Callback Not Firing: Debugging Silent Failures
A practical guide to diagnosing why your IntersectionObserver callback never fires — covering root causes from thresholds to root margins, with real debugging commands and war stories.
Service Worker Serving Stale Cache: Diagnose and Fix
A guide to debugging when a service worker returns stale cached responses instead of fresh data from the network.
SAML SSO Login Fails After IdP Metadata Update
A complete debugging guide for SAML SSO login failures, covering certificate rotation, assertion validation, and clock skew issues.
OpenID Connect ID Token Validation Failure Debugging
A practical guide to diagnosing and fixing OpenID Connect ID token validation failures, covering signature verification, expiration, issuer mismatch, and audience checks.
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.