
Pulsar
Distributed pub-sub messaging system
Coldcast Lens
Pulsar is what you reach for when Kafka's architecture starts fighting your requirements. It separates compute (brokers) from storage (BookKeeper), so you can scale each independently. Multi-tenancy is built-in, not bolted on. Geo-replication works across data centers. And it handles both streaming and queue patterns natively — no choosing between Kafka and RabbitMQ.
If you're building cloud-native, multi-tenant, or geo-distributed messaging systems, Pulsar's architecture genuinely fits better than Kafka. Kafka is still king for raw throughput — 15x faster writes and a massive ecosystem. RabbitMQ is the battle-tested choice for traditional task queues with complex routing. NATS is the lightweight option for microservices pub-sub.
The catch: Pulsar is complex. You're running brokers plus BookKeeper plus ZooKeeper (being removed) — that's three distributed systems to manage. Kafka's ecosystem is 10x larger: more connectors, more tooling, more engineers who know it. And Pulsar's throughput, while good, doesn't match Kafka's at the high end. For most teams, Kafka's operational simplicity wins.
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