Most importantly, I finally "got good" at MySQL and InnoDB. before this year I mostly looked at databases as magic put-stuff-in-and-query-it machines that always worked unless you were FAANG scale. Needless to say, that scaling boundary comes quite a bit earlier. The most interesting project by far was to limit query load of a big background job by implementing feedback control based on the disk throughput. I have a blog post written about it but the approval gears of the PR department can turn slow sometimes :)

Other things learned at work this year: Docker and Kubernetes. Not something I would have learned on my own, but in the end I'm glad I took the plunge since they're both pretty fascinating.

Outside of work: I finally got proficient with monadic parsing in Haskell. Parser combinators are simply the best parsing experience I've ever had and I really hope never to write another regex in my life.