A GlobalKTable broadcasts an entire table dataset to every Kafka Streams task as an immutable, read-only view. It enables fast lookups without the copartitioning constraints required by ordinary stream-table joins. section 8.3.6
Use the architectural trade-off deliberately:
- A new stream record triggers the join and can produce a result when matching table data exists. section 8.3.6
- A table update does not reprocess previously handled stream records. section 8.3.6
- Broadcast the table when its complete dataset can be made available to all tasks; otherwise, ordinary joins require matching partitioning and keys. section 8.3.6
Order lookup
When an order arrives, the application looks up corresponding customer data in the GlobalKTable. A match produces an aggregated result; a missing key produces no output. section 8.3.6
