In a cluster of Mule runtimes, where are persistent queues backed?

In a cluster of Mule runtimes, persistent queues are backed by the cluster's distributed data grid. This approach allows for high availability and reliability since the data is replicated across different nodes within the cluster. Utilizing a distributed data grid ensures that if one node goes down, other nodes within the cluster can continue processing messages in the queue without any loss or degradation of service.

This setup optimizes resource use and supports seamless message processing across the clustered environment, making it resilient to failures. Persistent queues are crucial for managing message flow and ensuring that messages are not lost even in cases of system crashes or network issues. By leveraging the distributed nature of the data grid, MuleSoft can maintain the integrity and availability of message data across the cluster.

The other options don't utilize the full benefits of a cluster setup. For instance, backing queues in an external database could introduce latency or single points of failure, while relying on local disk storage limits scalability and resilience across multiple runtimes. Using a cloud service provider might imply a dependency on external systems which could complicate the architecture and introduce overhead. Therefore, the choice of a distributed data grid within the cluster is optimal for persistent queues.