What is true about replicas ?
Replicas are passive - they don't handle produce or consume request. Produce and consume requests get sent to the node hosting partition leader.
To continuously export data from Kafka into a target database, I should use
Kafka Connect Sink is used to export data from Kafka to external databases and Kafka Connect Source is used to import from external databases into Kafka.
Where are KSQL-related data and metadata stored?
metadata is stored in and built from the KSQL command topic. Each KSQL server has its own in-memory version of the metastore.