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.
Debugging Cypress Tests Inside an iFrame: The Cross-Origin Trap
A practical debugging guide for when Cypress tests fail inside iframes—covering cross-origin restrictions, timing issues, and element access.
Cypress intercept stub not intercepting requests — debugging guide
A debugging guide for when cy.intercept() stubs silently fail to match or intercept requests, covering URL patterns, method mismatches, timing, and aliasing traps.
React Testing Library fireEvent Not Triggering: Silent Failures and Real Fixes
When React Testing Library's fireEvent doesn't trigger, it's usually due to stale closures, wrong event type, or async state updates. This guide covers real causes and fixes.
MSW Request Not Intercepted: Why Your Handler Isn't Catching the Call
A practical guide to debugging why MSW (Mock Service Worker) handlers fail to intercept requests, covering worker registration, URL mismatches, and lifecycle issues.
GraphQL Resolver Not Being Called: How to Diagnose and Fix
A practical guide to diagnosing why a GraphQL resolver isn't executing, covering schema mismatches, null bubbling, authentication filters, and resolver registration issues.
GraphQL Variable Type Mismatch Error Debugging
How to diagnose and fix GraphQL variable type mismatch errors caused by null handling, enum coercion, and schema mismatches.
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.