Couldn't you use Erlang/OTP for the main parts of the system and for the performance critical parts that Erlang isn't great for (like crunching numbers) you can

Couldn't you use Erlang/OTP for the main parts of the system and for the performance critical parts that Erlang isn't great for (like crunching numbers) you can use something like Rustler to be build a safer NIF? https://github.com/hansihe/rustler https://github.com/hansihe/rustler