For the most part there are similar caveats to .Net as anything else... you want to remain as stateless as possible at the request level, and you want to avoid blocking on IO as much as possible. There are async versions of most things, and you just have to use them... It's easy to do things that will sink you.

.Net and .Net Core can do API services very well, and can scale very well. It doesn't mean you can't still shoot yourself in the foot easily.