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.
Jest Module Mock Not Working: A Debugging Guide
A practical debugging guide for when Jest's jest.mock() doesn't actually mock the module, covering hoisting issues, path mismatches, and module caching.
Jest Fake Timers Not Advancing — Why setTimeout/setInterval Never Fire
A firefighting guide for when Jest's fake timers stall — timers don't advance, tests hang, or assertions time out. Covers the real root causes like legacy vs modern timer API, async gaps, and jest.useFakeTimers() placement.
Jest Async Test Timeout Exceeded: Root Causes and Debugging Steps
A practical guide to diagnosing and fixing Jest async test timeouts, covering promise hanging, done() misuse, and timeout configuration.
Vitest Coverage Not Collecting: Debugging Empty or Missing Coverage Reports
A direct guide to diagnosing why Vitest coverage reports come empty or missing, with concrete commands, config checks, and a real incident walkthrough.
Playwright Locator Not Found: Selector Timeout & Element Resolution
Diagnose and fix Playwright's 'locator not found' error with concrete debugging steps, common causes, and a production war story.
Playwright route.intercept Not Working: Silent Failures and Missing Requests
When route interception silently fails in Playwright, requests pass through unmodified. This guide covers real causes: glob patterns, method scope, page lifecycle, and route handler ordering.
Long-form thinking on debugging habits, observability, and the systems around the bug.
How to Read Error Messages: A Debugging Protocol
Most engineers skim error messages and miss the signal. Here's a repeatable protocol for extracting maximum information from stack traces, log lines, and crash dumps — with a real incident walkthrough.
When to Escalate a Bug: A Decision Framework for Junior and Mid-Level Engineers
A practical framework for junior and mid-level engineers to decide when to escalate a bug, with real-world examples and criteria beyond time spent.
Debugging vs. Firefighting: Why Treating Production Incidents as Debugging Sessions Fails
When production goes down, your brain wants to debug. That instinct costs you hours. Here's why firefighting requires a fundamentally different approach, and the specific process I use to switch modes.
Writing an Incident Runbook That Actually Gets Used in Production
A runbook isn't a document—it's a tool. Here's how to write one that reduces MTTR and doesn't embarrass you during the next PagerDuty alert.
Debugging a production incident with your boss on Slack: staying rational when everything is on fire
A personal account of debugging a cascading Redis failure while the VP of Engineering watched, and the mental models that kept the fix from turning into a rollback.
Reading Distributed Traces to Find Latency: A Field Guide
Tracing tools generate a firehose of data. Here's how to filter the signal from the noise and actually find the root cause of high latency.