It'd be immensely more helpful if you give Elixir library/framework names as alternatives to the technology names you enumerated. In textual form.
In fact, Mike Perham himself (the creator of Sidekiq) is asking the question how do you do scheduled future background processing in Elixir, right in this thread: https://news.ycombinator.com/item?id=12072359
There was a post about their usage of Elixir on the ElixirForum recently: https://elixirforum.com/t/complex-open-source-phoenix-apps-t...
https://speakerdeck.com/mosic/elixir-at-evercam?slide=6
Make more sense now? :) (in addition to the other responses)
tl;dr Evercam replaced Node.js, Sidekiq, Pusher and Upstart with Elixir, huge net gain in stack simplicity which is arguably a strong plus from a long-term maintenance perspective.