Hi! What happens to messages that are sent using a Pulsar producer during a Pulsar broker temporary outage? Are they stored in a producer backlog/queue until the broker is back up? are there settings to configure this? The producer also disconnects/crashes when the broker is unavailable?

The producer does not crash. Messages are buffered in an in-memory pending queue on the client and are automatically re-sent when the broker comes back, but only if they have not hit the 30 second send timeout first. That timeout, not the queue size, is what usually causes message loss during an outage and you can configure it.