we are actually doing precisely the same thing at instacart (breaking our 1+ million lines of code monolith into discrete components, which we call "domains"), and typing the boundaries and as much of the internals of these domains as possible with sorbet types.

this has the benefit of ruby dynamicism (fast development within domains, you can use all the nice railsy tooling, activerecord, and all the libraries we've built over the years), with type safety at the boundaries (we've also put in timeouts, thread separation, and error handling at the boundaries).

the additional benefit for using sorbet is that it makes making typed RPC calls (over twirp or graphql) much easier as you can introspect the boundaries trivially.

really cool to see other companies evolving similarly given the same starting conditions!