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.
Documenting Bugs: A Postmortem-Driven Approach That Cut Recurrence by 60%
Most bug write-ups are useless. Here's a structured, postmortem-driven approach that reduced bug recurrence by 60% in our team — with templates and a real incident walkthrough.
Debugging Inside Docker Containers: Tools, Techniques, and a War Story
Practical techniques for debugging inside Docker containers: exec, nsenter, strace, and a real incident that made me rethink debug images.
kubectl logs: Debugging Pods with Logs, Timestamps, and Previous Instances
Beyond `kubectl logs pod-name` — using timestamps, previous instances, and multi-container patterns to diagnose real failures.
Debugging Serverless Functions Locally: A Practical Approach
Local debugging of serverless functions requires different tools and mindset than traditional apps. Here's how I approach it with real examples.
Debugging Terraform and CloudFormation Errors: A Field Guide to the 3 AM Page
Infrastructure-as-code errors are inevitable. Here's how to systematically debug Terraform and CloudFormation failures without losing your mind.
Debugging as Hypothesis Testing: A Mental Model for Systematic Root Cause Analysis
Most debugging is frantic guessing dressed up as experience. Here's a mental model that treats debugging as a scientific process — form hypotheses, design experiments, and isolate root causes systematically.