One of my favorite bits from Tim's videos was during a tour of Firefly Aerospace's facility when they talk about engine cooling. They discuss EDM machining small holes into the coolant channels just before the throat, which lets a small amount of cryogenic coolant out to cool the interior. The funny part is that you can purposefully undersize the holes and they will melt larger until they are big enough to adequately cool the engine. You basically pre-season the engine with a test-fire and let it choose how much internal cooling it needs.

https://youtu.be/ac-V8mO0lWo?t=2203