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.
3 playbooks in Data & Storage
Debugging Pagination Bugs
Pagination bugs hide in boundary math, cursor reuse, and new records arriving between pages.
Debugging Transaction Rollback Issues
How to find partial writes when multi-step database workflows fail mid-request.
Debugging Database Consistency Bugs
How to trace query consistency issues across repositories, replicas, and API response contracts.
Structured investigations for the failure modes engineers meet in real systems.
SQLAlchemy N+1 Queries: Diagnosing Lazy Loading Performance Disasters
How to detect, diagnose, and fix the N+1 query problem in SQLAlchemy caused by lazy loading. Includes concrete commands, SQLAlchemy event hooks, and realistic war stories.
Pandas dtype Unexpected Conversion: A Debugging Guide
When pandas silently changes dtypes from int to float, object to category, or datetime to object, debugging requires understanding pandas' internal type inference and nullable integer arrays. This guide covers real-world causes and fixes.
Debugging redis-py Connection Refused Errors
A step-by-step guide to debugging 'Connection refused' errors in redis-py, covering network checks, Redis config, and Python client troubleshooting.
Spring JPA LazyInitializationException: Root Causes and Fixes Beyond OpenSessionInView
A practical guide to diagnosing and fixing LazyInitializationException in Spring Data JPA, covering real-world causes like serialization, caching, and transaction boundaries.
Hibernate N+1 Select Problem: Detection, Diagnosis, and Fixes
A hands-on guide to detecting and fixing the Hibernate N+1 query problem with real SQL profiling, lazy loading traps, and JPA fetch strategies.
GCP Firestore Query Needs Index: Diagnosing and Fixing the Missing Index Error
A focused guide to diagnosing and fixing the 'index required' error in Google Cloud Firestore queries. Covers composite index creation, query structure pitfalls, and debugging with real examples.
Long-form thinking on debugging habits, observability, and the systems around the bug.
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.
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.
The Real Cost of N+1 Queries: More Than Just Slow Pages
N+1 queries are often dismissed as a minor performance issue, but their real cost goes far beyond slow page loads—think cascading timeouts, database meltdowns, and cloud bills that balloon overnight. Here's what you're actually paying for.