Replaceable with what? There has to be some method of specifying background tasks that run for Discourse to function.
Anyway 1GB RAM works absolutely fine for most Discourse sites, we have literally dozens of $99 installs running 1GB RAM on Digital Ocean with zero issues whatsoever. You won’t need more than 1GB RAM unless your Discourse is especially large or especially active, so I’m not sure what the benefit would be of replacing Sidekiq, exactly?