Only one of the replicas is elected as partition leader. And a broker can definitely hold many partitions from the same topic on its disk, try creating a topic with 12 partitions on one broker!

SHOW STREAMS and EXPLAIN <query> statements run against the KSQL server that the KSQL client is connected to. They don't communicate directly with Kafka. CREATE STREAM WITH <topic> and CREATE TABLE WITH <topic> write metadata to the KSQL command topic. Persistent queries based on CREATE STREAM AS SELECT and CREATE TABLE AS SELECT read and write to Kafka topics.
Non-persistent queries based on SELECT that are stateless only read from Kafka topics, for example:
SELECT A FROM foo WHERE A;
Non-persistent queries that are stateful read and write to Kafka, for example, COUNT and JOIN. The data in Kafka is deleted automatically when you terminate the query with CTRL-C.

Using Future.get() to wait for a reply from Kafka will limit throughput.

Replicas are passive - they don't handle produce or consume request. Produce and consume requests get sent to the node hosting partition leader.

AGlobalKTableis a replicated, read-only table available in full on all instances. It's best forreference or lookup datasetssuch as:
* Product catalog
* Customer profiles
* Warehouse inventory
FromKafka Streams Developer Guide:
"Use GlobalKTable when you need to perform joins using non-partition-aligned reference data that's small enough to replicate."
* Purchases and transactions are high-throughput, time-sensitive streams, not static reference data.
Reference:Kafka Streams Concepts > GlobalKTable