The integrations gateways are built into HTTP services, so the Director is an HTTP client to those gateways. (The image under "All Together Now" omitted our integrations gateways -- architecturally, they lie between the Director and the actual third-party API endpoints.)

i don't understand. presumably the go code just makes an http call? what makes you think you can't do the same in erlang?

I don't know much about Erlang - wouldn't it be able to interface with HTTP in the same way?

Erlang certainly can be used to implement an HTTP client, but once you step outside of Erlang's actor model and virtual machine, you lose those benefits that it provides in terms of message passing behavior.

(the state of http clients on Erlang is also pretty abysmal.)