What I look for in an oncall handoff

I split a 4000-line file into 12 smaller ones this week. The smaller files weren't actually easier to understand. The 4000-line file was a problem of structure, not of length.

Most of the trouble I see in production comes from boundary cases someone promised would never happen. The code is fine. The plan is fine. The promise is what ages badly.

If a config file has more than a dozen options, half of them aren't being used. The other half are being used in ways the original author didn't predict.

The team I learned the most from didn't have great tools. They had a great habit of reading each other's pull requests in full, including the parts that weren't theirs.

Most retry logic I've removed turned out to be hiding a real bug. The retries made the failure invisible, and the bug compounded for months in the background.