sorry! so I'll clarify
Elixir inherits a library called OTP from erlang which is a set of primitives for building massively concurrent systems.
A Genserver is sort of like a Base Class for a object that runs as an independant process that plugs into OTP. By inheriting/implementing the Genserver behavior, you create an independant process that can be mounted in an OTP supervision tree which runs at the top of your application and monitors everything below it. Out of the box, that means your process can be sent messages by other processes and can send messages itself. If a crash happens, the supervisor will kill it, resurrect it and redirect messages to the new process.
Creating a Genserver is as easy as adding an annotation and implementing a few callbacks.
Genservers are the base on which a lot of other systems build on. Oban, a job worker essentially builds on Genserver to use a postgres table as a job processor. Since its just a Genserver with some added behavior, adding a background worker is as simple as adding a file that inherits from Oban and specifying how many workers for it should be allocated in a config file. The result is that adding a background worker is about as much work for me as adding a controller. No additional work for devops either.
And yes, it is very sci fi. Honestly I'm shocked elixir isn't more widespread. there's very little hype behind it but the engineering is pretty solid. Every scaling bottleneck we've had so far has been in the database (only because we particularly make heavy use of stored procedures)