[josevalim]

Your web server, database connections, http clients would be the ones leveraging OTP here. In my talks, I usually cover the design of the connection pool and how it guarantees bugs in the pool bring all connections down with it, without leaking resources.

Ideally, developers should be able to use Phoenix for simple applications without caring about the low-level OTP details. That's how we tried to structure the Phoenix book: the classic MVC and then the OTP stuff. But it seems we still have more work to do in this area. :)