[alangpierce]

"Backend worker" is a pretty generic term, and I think in this context it just means any server that isn't a web server or API server. Examples:

* A "users" microservice in a microservice architecture might load relevant information and permissions about the current user. A web or API server that's directly handling a user request would call that microservice for more information.

* In response to some user action, a task is sent to a task queue to do follow-up processing, e.g. reindexing any changed data. The task queue system sends the task to some worker process that specifically is there to handle tasks.

* A daily cron job on a dedicated machine sends an email to everyone who signed up between three and four days ago.

[zappo2938]

It seems that people are using different phrases and words for the similar things, i.e. message broker, message queue, message pipline, message bus, microsevice, service, backend worker, task queue.