Explain advanced background job processing architecture using queues in PHP systems.

Background job systems decouple heavy or asynchronous tasks from request-response flow using queue-based processing.

PHP systems use queues to handle long-running tasks asynchronously.

Queue components:

Push jobs into queue.

Redis, RabbitMQ, Kafka.

Consume and process jobs.

Patterns:

Jobs may run multiple times.

Jobs must handle duplicates safely.

Failed jobs isolated.

Important jobs processed first.

Scheduled execution.

Challenges: