I’ve built monoliths but never at scale, but don’t see why they wouldn’t have scaled incredibly well. I have built macroservices that have scaled super well (5ish services IIRC).
I think it comes down to how you define a microservice/monolith. when it comes down to codebase, our codebase is very much a monolith. however elixir lets you connect nodes together and setup individualized processes that can be communicated with by any other node in your network toplolgy using the BEAM's built in pubsub system. in essence, creating a new microservice is easy. you just define a geneserver file and add it to your application.ex. about as much effort as adding a controller in rails and that makes a big difference. you get a lot of the advantage of microservice architecture where you spread computation across your physical machines but the codebase is a small easy to maintain monolith.