Redis Streams
Append-only stream data structure in Redis — like a lightweight Kafka. Consumer groups, XADD/XREAD/XACK commands. Added in Redis 5.0 (2018).
Antirez's answer to "people use Redis pub/sub for things that should be Kafka". Strength: simple, fast, low ops overhead. Weakness: limited by memory size, not built for huge replay scenarios. Great for in-app event buses, job queues with replay, simple CQRS. Competitors: NATS JetStream, Kafka, Pulsar.