Why it matters

Understanding Pulsar's architecture helps pick between it and Kafka. Neither is universally better; use case matters.

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The architecture

Broker: serves clients, routes to storage. Stateless.

BookKeeper (bookies): storage layer. Data lives in ledgers.

ZooKeeper: coordination.

Pulsar architectureBroker (compute)stateless routingBookKeeper (storage)ledgersZooKeepercoordinationCompute-storage separation enables independent scaling; Kafka bundles both
Pulsar layers.
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How it works end to end

Topics: partitioned like Kafka. Also non-partitioned topics.

Subscription types: exclusive, shared, failover, key-shared. Different semantics than Kafka consumer groups.

Geo-replication: built-in cross-cluster replication.

Tiered storage: offload old data to S3 automatically.