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.
JavaScript Long Task Blocking Main Thread: Diagnosis and Fixes
A practical guide to identifying and fixing JavaScript long tasks that block the browser's main thread, causing jank and poor user experience.
Debugging High Interaction to Next Paint (INP) Scores
A practical guide to diagnosing and fixing poor Interaction to Next Paint (INP) scores, covering event handler delays, rendering bottlenecks, and real-user monitoring.
Service Worker Serving Stale Content: A Debugging Guide
Diagnose and fix service workers that refuse to update cached assets, leaving users stuck on old JavaScript bundles or stale API responses.
Debugging JavaScript Garbage Collection Pauses That Kill Responsiveness
Learn how to identify and fix long GC pauses in Node.js and browser JavaScript using Chrome DevTools, Node --trace-gc, and heap snapshots.
OpenTelemetry Traces Not Appearing: Debugging Missing Spans in Production
A debugging guide for when OpenTelemetry traces are not appearing in your observability backend. Covers common and non-obvious causes like sampling misconfiguration, exporter timeouts, and context propagation failures.
Node.js CPU Profiling: Fixing a Stuck Event Loop in Production
A practical guide to diagnosing Node.js CPU spikes using flame graphs, perf, and async hooks. Includes a real incident where a JSON serialization loop blocked the event loop for 12 seconds.
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.