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.
Next.js Image Component Fails to Optimize Images
Diagnose and fix root causes when Next.js <Image> skips optimization. Covers config, domains, loader issues, and CDN missteps beyond the basics.
React List Rendering: Diagnosing and Fixing Key Prop Warnings
How to debug and resolve React's list key prop warnings, including subtle runtime issues beyond console noise. Concrete steps, root causes, and real-world incident.
Next.js Static Site Generation Build Failures: Diagnosing getStaticProps and getStaticPaths Issues
Concrete diagnosis and fixes for Next.js static generation (SSG) build failures, covering getStaticProps, getStaticPaths, missing data, and non-obvious traps.
Diagnosing `ref.current` Is Null in React
A practical guide to tracing and fixing cases where a React ref's `current` is unexpectedly null, including async pitfalls and strict mode quirks.
Diagnosing and Resolving Next.js Server Action Errors
Pinpoint and fix errors in Next.js server actions, focusing on non-obvious causes like serialization and environment mismatches.
Diagnosing React Router Infinite Redirect Loops
How to fix and prevent infinite redirect loops in React Router—pinpoint the logic errors, misconfigurations, and unexpected auth flows that cause them.
Long-form thinking on debugging habits, observability, and the systems around the bug.
Mocking External APIs in Tests: Why stubbing HTTP is harder than it looks
Stubbing HTTP calls seems easy until a subtle mismatch between your mock and the real API causes a production incident. Here's what I learned the hard way.
How I Diagnosed a 1-in-1000 Race Condition in Our CI Pipeline
A race condition that only appeared once every thousand CI runs took weeks to track down. Here's how we finally caught it, what tools helped, and what we changed to prevent similar bugs.
How Database Indexes Work: A Debugging Story
A practical guide to understanding database indexes through the lens of debugging a real production outage caused by a missing covering index.
Reading PostgreSQL EXPLAIN ANALYZE Output: A Practical Guide with Real Query Examples
EXPLAIN ANALYZE is the single most important tool for diagnosing slow queries. Here's how to read the output, spot common pitfalls, and fix them with real-world examples.
When caches lie: debugging stale data in distributed systems
Cache invalidation is often cited as one of the two hard problems in CS, but the daily reality is subtler: partial staleness, clock drift, and silent evictions. This post walks through real debugging techniques for stale data in Redis, Memcached, and CDN layers.
Debugging Cache Invalidation Failures: A Case Study with Redis and PostgreSQL
Cache invalidation sounds simple — write-through, TTLs, done. But in practice, silent failures hide in race conditions, connection pools, and stale read replicas. Here's a real debugging story with Redis and PostgreSQL that taught me how to find them.