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.
Debugging HPACK Errors in HTTP/2 Header Compression
A practical guide to diagnosing and fixing HTTP/2 header compression errors caused by HPACK implementation bugs, oversized headers, or compression context mismatches.
Nginx Upstream 503 Service Unavailable: A Production Debugging Guide
A practical guide to diagnosing and fixing Nginx 503 errors caused by upstream failures, including connection limits, timeouts, and health check misconfigurations.
Debugging Nginx Rate Limiting 503 Errors
A practical guide to diagnosing and fixing 503 errors caused by Nginx rate limiting, with concrete commands and real-world scenarios.
SameSite Cookie Attribute Blocking Requests: Debugging Guide
A practical guide to diagnosing and fixing request failures caused by the SameSite cookie attribute, including cross-site and same-site nuances.
CSRF Token Validation Failed: Real-World Debugging Guide
A practical debugging guide for CSRF token validation failures in web applications, covering root causes, diagnosis, and fixes beyond the textbook.
Content Security Policy Blocking Resource: Debugging and Fixing CSP Violations
A direct guide to diagnosing and fixing CSP violations when resources like scripts, styles, or images are blocked by Content Security Policy headers.
Long-form thinking on debugging habits, observability, and the systems around the bug.
Why Your P99 Latency Is Lying to You (and What to Use Instead)
The 99th percentile is the go-to metric for tail latency, but it's easy to fool. Here's a real outage caused by trusting P99, and how to build a more honest monitoring stack.
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.
Reading Flame Graphs: The Non-Obvious Patterns That Reveal Real Bottlenecks
Flame graphs are everywhere in performance profiling, but most engineers only scratch the surface. Here are the patterns that actually tell you where your code is slow.
Print Debugging vs Debugger: When printf Wins and When It Fails
Printf debugging is dismissed as primitive, but in many real-world scenarios it's faster and more reliable than a full debugger. Here's the tradeoff with concrete examples from distributed systems and production incidents.
Writing Postmortems That Actually Improve Reliability
A postmortem that blames someone gets filed and forgotten. A postmortem that traces cause without blame becomes a reliability upgrade. Here's how to write the second kind, with a real example from an 18-hour DNS outage.
Feature Flag Debt: When Your 500 Conditional Branches Become the Incident
Feature flags are great until they're not. Here's how to audit, remove, and automate cleanup before your 500th conditional branch becomes the root cause of a production incident.