7.3 Consumer Groups, Durability, and Choosing a Broker

Three systems carry the same order workload in this comparison: an order service publishes 5,000 events per second of about 1 KB each, and a billing service and an analytics service both consume them. The previous lesson compared them on what follows from what each one is. Kafka is a replicated log on disk with the highest sustained volume and replay over days or more. SQS is a managed task queue with elastic volume and no replay, and Redis Streams is an in-memory log whose retention is bounded by RAM, at about 5 MB per second or 18 GB per hour for this workload.