MicroVMs
The CORS Header Is Present Twice and That Is Why It Fails
You added the header at the proxy, your framework was already sending it, and the browser now rejects both. Duplicates are invalid, not additive.
MicroVMs
413 Request Entity Too Large When You Already Raised the Limit
You raised the body size limit and the upload still fails. There are almost always two limits, and the one you changed is rarely the one rejecting you.
MicroVMs
The Service Is Running, Listening, and Completely Unreachable
curl works on the box and hangs from outside. Four places the packet can die, and how to tell which one killed it without guessing.
Networking
TLS Handshake Failures: the Error the Server Actually Sent
handshake failure, protocol version, unknown ca and bad certificate all mean different things. Here is how to get the real reason out of a connection that…
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
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 526: The Redirect Loop Behind 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; 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 Serves Stale Data and the Bug Is 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.