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.
GraphQL Subscription WebSocket Not Receiving Events
A step-by-step debugging guide for when GraphQL subscriptions fail silently over WebSocket—no events, no errors, just silence.
Apollo Client Cache Not Updating After Mutation: How to Force a Normalized Cache Refresh
If Apollo Client returns stale data after a mutation, your normalized cache isn't merging correctly. Here's how to diagnose cache policies, field merge functions, and cache redirects.
Svelte Store Not Updating Component – Reactive Assignment Pitfalls
Learn how to debug a Svelte store that doesn't trigger component re-renders. Covers reactive assignments, store subscriptions, and common Svelte reactivity gotchas.
Debugging Apollo Federation Subgraph Errors: A Field Guide
A practical guide to diagnosing and resolving errors from Apollo Federation subgraphs, including type resolution failures, entity lookup issues, and gateway-subgraph communication problems.
Svelte Reactive Statement Not Re-running After State Change
A deep guide to debugging Svelte reactive statements that fail to re-run: covering dependency tracking pitfalls, stale closures, and assignment traps.
SvelteKit load function errors: root cause analysis and fix patterns
A practical guide to diagnosing and fixing errors in SvelteKit load functions, covering server vs client context, serialization issues, and timing pitfalls.
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.