Azure Event Hubs 6 is Microsoft's own partitioned log, older than its Kafka 129 support, and it is not Kafka inside. Its Standard, Premium and Dedicated tiers (not Basic) expose an endpoint that speaks the Kafka protocol, version 1.0 and later, so Kafka clients connect by changing configuration only. The concepts map one to one: a namespace is the cluster, an event hub is a topic, and partitions, consumer groups and offsets keep their names. Every connection uses TLS on port 9093 and SASL, either OAuth 2.0 tokens from Microsoft Entra ID (OAUTHBEARER, recommended, with Azure 6 RBAC roles instead of ACLs), or a shared-access connection string sent through PLAIN, with the literal user name $ConnectionString and the connection string as the password.
Compatibility is good for producers and consumers and partial beyond them. Transactions and the Kafka Streams 129 library are in public preview, only on Premium and Dedicated; compression works only there and only with gzip; log compaction is supported, with a cap per partition of 1 GB on Standard and 250 GB on Premium. There is no managed Kafka Connect 129 : point your own Connect workers at the namespace, or use Azure's integrations (Capture to storage, Stream Analytics). The newer protocol features of this chapter (KIP-848 groups, share groups) are not on its feature list, and its overview page still says Kafka lacks the competing-consumer queue pattern, which Kafka 4.2's share groups (Consumers and Queues) now provide.
| Tier | Capacity price (East US) | Retention | Message size | Partitions per hub |
|---|---|---|---|---|
| Standard | $0.03 per TU-hour + $0.028 per million events | 7 days | 1 MB | 32, fixed |
| Premium | $1.027 per processing unit-hour | 90 days | 1 MB | 100 |
| Dedicated | $6.849 per capacity unit-hour (4-hour minimum) | 90 days | 20 MB | 1,024 |
A throughput unit (TU) allows 1 MB/s or 1,000 events/s in and 2 MB/s out, and events are billed in 64 KB units. One Standard TU for BookNest costs about $22 a month, by far the cheapest of the three, with one serious catch: Standard keeps events at most 7 days, so the replayable 18-month history of Retention and Compaction (retention.ms=-1) is impossible there. Premium keeps 90 days for about $750 a month per processing unit; for longer history, Capture writes the events to Azure storage for the lakehouse (Lakehouses, Data Quality and Governance).