MicroVMs
The Domain Resolved Everywhere Except Where I Was Sitting
A CNAME that dig confirmed, a browser that refused, and a certificate stuck on pending. Three separate caches pretending to be one problem.
DevOps
Your systemd Service Will Not Start and the Logs Say Nothing Useful
status=203/EXEC, status=217/USER, and the other exit codes that mean something specific. Here is how to read them and what each one actually points at.
Networking
Cloudflare Error 526 and the Redirect Loop: Two Failures, One Setting
Flexible gives you an infinite redirect. Full strict gives you a 526. The documentation says Full or higher, and higher is the one that breaks.
Shopify
Shopify Webhooks You Are Not Receiving
The webhook is registered, orders are being created, and nothing arrives. Here is where they go and how to stop being unsubscribed.
Bug Hunt
A 400ms Latency Spike That Turned Out to Be DNS
p99 jumped on one service. The database was fine, every dependency reported healthy, and the flame graph pointed at nothing. That turned out to be the clue.
Networking
Your Webhook Handler Will Be Called Twice and You Should Plan For It
At-least-once delivery means duplicates are normal operation, not an edge case. Here is how to build a handler that survives them.
Databases
Your Cache Is Serving Stale Data and the Bug Is in the Invalidation
Reading from cache is easy. Knowing when to remove something is where the bugs live, and most of them are races.
Networking
GraphQL Returns 200 With Your Error Inside It
Every response is a success as far as HTTP is concerned. That one design decision breaks monitoring, retries, and error handling unless you plan for it.
Networking
redirect_uri_mismatch and the Rest of OAuth Debugging
OAuth errors are unhelpful by design, because detailed errors would help attackers too. Here is how to work out what is actually wrong.
Networking
429 Too Many Requests: Both Sides of Rate Limiting
How to handle being rate limited without making it worse, and how to implement limits that do not punish well behaved clients.
Kubernetes
Debugging DNS Inside Kubernetes When nslookup Lies
nslookup resolves and your application cannot connect. The two use different resolvers, and the difference is where the bug lives.
Networking
Your Timeouts Are Wrong and Here Is How to Set Them
A missing timeout turns a slow dependency into an outage. A badly chosen one turns a blip into a retry storm. Both are common.