The easiest way to discover a background job is to notice that a request is trying to do too much. A user clicks once, but the server wants to generate something, call another service, update several records, and wait for all of it to finish.
Look for time, retries, and independence
If the operation takes long enough that the user should not wait for it, can fail independently, or can be retried safely, it is a good candidate for a queue.
Make progress visible
Moving work off the request is only half the feature. The user still needs a useful state: queued, processing, complete, or failed. A simple status model is often better than trying to stream every internal detail.
A queue is not a faster request. It is a different contract.
Start with one worker
You do not need an elaborate distributed system on day one. One durable queue, one worker, and an idempotent job handler can take you surprisingly far.
Once the job has a clear input, output, and retry policy, the rest of the infrastructure becomes much easier to reason about.