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 Backend & APIs
Debugging Retry Bugs
Retry issues often hide the first failure and create duplicate work.
Debugging Idempotency Bugs
How to debug duplicate writes when clients, webhooks, or workers retry after ambiguous failures.
Debugging Payment Races
How to reason about duplicate charges, concurrent refunds, and payment workflow compensation.
Structured investigations for the failure modes engineers meet in real systems.
CORS error after deployment: how to debug it
API works fine in dev but browsers block requests after deploy with a CORS error. Find the origin mismatch and fix it.
API returns 404 after deploy: how to debug it
Your API endpoint works locally but returns 404 after deployment. The route is in your code — the server just cannot find it.
API returns 500 only in production: how to debug it
Your API endpoint returns 200 locally but 500 in production. Some code path that never triggers in dev fires in the real environment.
Idempotency key not preventing duplicate payment: how to debug it
Your payment API accepts an idempotency key but still processes the same charge twice. The key is not being checked, stored, or matched correctly.
Rate limit bug: how to debug unexpected rate limiting issues
Legitimate users are hitting rate limits. The limiter is too aggressive, counting wrong, or sharing state across instances when it should not.
API timeout: how to debug request timeout issues
Your API endpoint returns a timeout error. The request takes longer than the configured timeout, but the operation might have succeeded silently on the server.
Long-form thinking on debugging habits, observability, and the systems around the bug.
Debugging Third-Party API Issues: A Systematic Approach
A practical guide to diagnosing and fixing third-party API integration problems, with real-world examples and a step-by-step debugging framework.
Debugging Webhook Delivery Failures: What the Logs Don't Tell You
HTTP 200 doesn't mean your webhook was processed. A practical guide to the network and middleware layers that silently drop webhooks.
Debugging HTTP Headers with curl: From Basic Flags to Packet-Level Inspection
A practical guide to inspecting HTTP request and response headers with curl, covering basic flags, debugging tricky issues, and understanding what your headers are really doing.
Debugging WebSocket Real-Time Features: Packet Loss, Reconnect Storms, and Silent Failures
WebSocket debugging goes beyond console.log. I cover packet capture with tcpdump, reconnect backoff strategies, and a war story about a silent failure that took down a production chat feature.
Rest API Design Mistakes That Inject Bugs Into Your System
Most API bugs aren't in the implementation—they're baked into the contract. Here are the design errors I've seen cause the most production incidents.
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.