Which message broker supports ordering guarantees and exactly-once delivery at high throughput?

A common choice is Apache Kafka.

• Ordering guarantees: Kafka preserves message order within a partition.
• Exactly-once delivery: Kafka supports exactly-once semantics (EOS) for processing pipelines when configured properly.
• High throughput: It’s designed for very high throughput and low-latency streaming.

If you need global ordering, that’s typically harder at high throughput in any broker; Kafka usually achieves ordering per partition, so you’d design your key/partitioning strategy around that.