Can you explain the main differences between the backend and broker parameters in Celery?

In Celery, the parameters backend and broker are responsible for different aspects of the system's operation:

• broker — is an intermediary for message passing between the client and workers. It manages the task queue. Usually, this is RabbitMQ, Redis, or another message broker. The client sends a task to the broker, and workers retrieve tasks from the broker for execution.

• backend — is a system for storing the results of task execution. After a task is completed, its result is saved in the backend so that the client can retrieve it later. Databases, Redis, RPC, and others can be used as backends.

Example configuration:

app = Celery('tasks', broker='redis://localhost:6379/0', backend='redis://localhost:6379/1')

Here, Redis is used both as a broker and as a backend, but on different databases (0 and 1).