How is Sidekiq different from ActiveJob in Rails?

Question

Ruby on Rails

I'm new to using background tasks, there's one thing I can't figure out.
Delayed - resque - sidekiq - one gang, analogues to each other.
But where is ActiveJob located? If it is also an analogue of those things,
then how to understand the use of Sidekiq on top of ActiveJob?
And why sidekiq, if used separately, then tasks are created for it in app/workers,
and if used on top of ActiveJob, then in app/jobs?
And what is the best way to use Sidekiq: standalone or on top of ActiveJob and why?

Answer 1

ActiveJob is an abstraction over queue solutions (sidekiq, dj, rescue, you can write your own adapter).
If you use sidekiq through ActiveJob, it will be easier to switch to another option if something happens.
But some advanced sidekiq features will not be available ( https://github.com/mperham/sidekiq/wiki/Active-Job),