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.
FastAPI Dependency Injection Fails: Missing `async def` and Scope Mismatches
A practical guide to debugging FastAPI dependency injection errors caused by missing async def, incorrect scope, or parameter mismatches.
Django Celery Task Not Executing: A Field Guide to Silent Failures
Diagnose why your Celery task won't run in Django — from broker misconfigurations to worker crashes. Commands, logs, and fixes included.
Debugging FastAPI 422 Validation Errors: Pydantic Model Mismatches
A systematic approach to diagnosing and fixing HTTP 422 validation errors in FastAPI, focusing on Pydantic model mismatches and request parsing issues.
FastAPI Background Task Not Running: Debugging Silent Failures
A practical debugging guide for when FastAPI background tasks silently fail to execute, covering lifespan events, async context, and server configuration.
Debugging FastAPI CORS Errors from Frontend Requests
A practical guide to diagnosing and fixing CORS errors when a frontend makes requests to a FastAPI backend.
Python Multiprocessing PicklingError: How to Debug
A practical guide to diagnosing and fixing PicklingError when using Python's multiprocessing module. Covers pickling scope issues, lambda closures, and dynamic classes.
Long-form thinking on debugging habits, observability, and the systems around the bug.
The Art of the Minimal Reproducible Example: A Debugging Superpower
A minimal reproducible example (MRE) is more than just a snippet — it's a tool that isolates the bug, saves time, and gets you faster answers. Here's how to build one that works, with a real-world war story.
Retry Storms: When Retries Make a Cascading Failure Worse
Retries seem like a safety net, but in a distributed system under load they can turn a small hiccup into a full outage. Here's how retry storms form and what to do about them.
Caching Bugs Are the Worst: A Postmortem on Stale Data Disasters
A deep dive into the most insidious caching bugs, with real postmortems and practical patterns to avoid stale-data disasters.
Observability vs. Monitoring: Why Your On-Call Rotation Still Wakes You Up at 3 AM
Monitoring tells you something is broken. Observability lets you figure out why—without guessing, without SSH, without restarting the pod.
Debugging Flaky Tests for Good: A Systematic Approach to Root Cause Analysis
Flaky tests waste time and erode trust. Here's how to find and fix the actual root cause instead of just rerunning.
Idempotency Keys: The Safety Net Your Payment API Needs
How idempotency keys prevent double charges, lost refunds, and data corruption in payment APIs. With real-world examples and edge cases you haven't considered.