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.
Flaky tests in CI: how to debug and fix intermittent test failures
A test passes nine times out of ten but randomly fails in CI with no code changes. Flaky tests destroy trust in the test suite — here is how to find and fix them.
Stale cache key bug: how to debug cache key collisions
Your cache returns data belonging to a different user, tenant, or request. The cache key is not unique enough — it is missing a dimension.
Distributed lock not releasing: how to debug stuck locks
Your distributed lock is acquired but never released. The lock holder crashed, the TTL expired but the key lingers, or the unlock logic has a bug.
Idempotency key not preventing duplicate payment: how to debug it
Your payment API accepts an idempotency key but still processes the same charge twice. The key is not being checked, stored, or matched correctly.
Slow API response: how to debug latency issues
An API endpoint that used to return in 50ms now takes 3 seconds. Find the bottleneck before your users notice.
N+1 query slowing down your API: how to find and fix it
Your API makes one query to get a list, then one more query for every item in the list. That is the N+1 pattern — it turns 1 query into 101 and kills performance.
Long-form thinking on debugging habits, observability, and the systems around the bug.
Profiling SQL Queries: Finding and Fixing the Slow 5%
Profiling SQL queries is more than running EXPLAIN. This guide covers practical techniques to find the slowest queries, interpret execution plans, and fix them — with real examples from PostgreSQL and MySQL.
Debugging Character Encoding Problems: From Gibberish to Unicode
A practical guide to identifying and fixing character encoding problems, from broken UTF-8 to hidden BOM bytes, with real debugging examples.
Debugging Timezone Date Bugs: A Case Study in UTC vs. Local Time
A practical walkthrough of a timestamp bug that broke a billing system, with reproducible code and debugging tactics.
Floating Point Arithmetic Errors: A Debugging Postmortem
How a $0.0000000000000004 error silently corrupted a financial system, and the debugging techniques that caught it.
Why JSON.parse() Throws and How to Catch It: A Field Guide to Parsing Failures
JSON.parse() seems simple until it throws. Here's a practical guide to the most common — and most maddening — parsing failures I've encountered, with exact error messages and fixes.
Debugging Third-Party API Issues: A Systematic Approach
A practical guide to diagnosing and fixing third-party API integration problems, with real-world examples and a step-by-step debugging framework.