Actually I work primarily on web services. We benefit from Haskell in that HKTs allow us to model our service completely in the type system. Our Rest and GraphQL API are completely modeled in a type level DSL. Once we've ingested data, which can then be validated automatically using types, we can then express our data transformation in a way that makes the transitions extremely transparent in our code.

Our backend services are written in Rust for things that need efficient computation.

That sounds very interesting. Did you open source any parts of your code, write any blog posts about it or give any public talks about it? I would love to read/watch whatever you have available to the public :)

Sounds like the service in your case is a sessionless gateway that does data transformation and dispatching. It fits the functional style.

I do think this echoes fooyc's point though: this does not sound like an area that would benefit from OOP. Sounds like an ideal use-case for functional.

Looks like functional programming sweet spot: data transformation.