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.
Prometheus Alert Not Firing: A Systematic Debugging Guide
A structured approach to diagnosing why a Prometheus alert rule isn't triggering, covering expression evaluation, staleness, relabeling, and configuration pitfalls.
Sentry Not Capturing Errors: A Debugging Guide
A direct guide to diagnosing why Sentry fails to capture errors in production, covering SDK misconfigurations, network issues, and rate limits.
Distributed Tracing Spans Not Connecting: A Debugging Guide
Guide to debugging missing parent-child connections in distributed traces, covering sampling mismatches, header propagation failures, and clock skew.
Correlation ID Not Propagating Across Asynchronous Boundaries
Debug why your distributed logging correlation ID disappears across async boundaries, thread pools, or event buses — with concrete commands and fix patterns.
CDN Cache Not Invalidating After Deploy – Debugging Stale Assets
A practical guide to diagnosing and fixing CDN cache invalidation failures after deployments, covering common misconfigurations, header issues, and verification steps.
HTTP ETag and Cache-Control Not Caching: Why Browsers Ignore Your Headers
A practical guide to debugging HTTP caching failures when ETag and Cache-Control headers are present but browsers or proxies refuse to cache responses.
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.