Let me guess, they should rewrite everything in Javascript?

Woe is us if they actually did.

Nah, Excel. /s

Almost everyone embraced polyglotism and microservices together.

Meh. As long as you’ve got a good, typed interface for passing messages between them and for having a common understanding of (and versioning system for) key data structures, that’s fine for this sort of thing where it’s largely processing steams of small messages and events.

… but it’s probably JSON and some JSON-Schema-based “now you have two problems” junk instead of what I described. In which case, yeah, ew, gross. Unless they’ve made some unusually good choices.

There are tons of approaches to align on service contracts for JSON based API calls. There’s also libraries like gRPC which help make contacts explicit. Neither are really uncommon

What are some of those approaches? Are there formal methods and/or tools for doing this?