> sbt -- I still have a lot of coming up to speed to do here, but the manual is like 500 pages and it's somewhat overwhelming.

SBT is not worth it. Ignore it and use Mmaven.

> The functional side is fascinating -- I'm still studying the cats library. I can almost describe a Monad! It's a pretty big mountain, though, and there are times where I have doubts whether the benefits will be worth it. Would love to hear some re-assurance! ;)

You shouldn't use these things unless and until you need them. Cats is basically a library of techniques for letting you accomplish things that seem like they might need language features by instead writing plain old functions that return plain old values. If you use the fancy technique for the sake of using the fancy technique, you're putting the cart before the horse. You should use them where you'd otherwise have to use some weird language feature (exceptions, magic async, mutable variables...).

> * The ecosystem for microservices seems pretty closely tied to akka & lagom. These are quite complex in their own right and we've been having trouble with the latter in particular. Curious to learn about alternatives. ZIO?

Mostly you don't need anything too complex. I'd recommend using akka-http to start with, but don't use any akka proper - stick to the routing DSL level and use futures rather than actors. When you're more comfortable with the functional abstractions you can switch to http4s.

I learnt Scala before diving deeper into FP, but I think properly learning/understanding Monads and some other FP concepts greatly help every sort of programming I do (even though it is mostly OOP nowadays). You come to notice it everywhere and even if you can’t abstract over them (there is no one `bind` or `join` function, so it may be called different with each Monad instance), but after understanding them you will gain a better reasoning power over them.