Setting a group.id that's consistent across restarts will allow your consumers part of the same group to resume reading from where offsets were last committed for that group

A409 Conflictresponse in Kafka Connect REST API usually means:
* The connector name provided already exists (i.e., a connector with that name is already deployed).
* The Kafka Connect cluster is temporarily unavailable to accept new tasks due toa rebalance in progress.
From theConfluent Developer documentationand Kafka Connect REST API spec:
"409 - Conflict. The connector name is already in use or the worker group is in the process of rebalancing and cannot complete the request at this time." Option A is incorrect because invalid configurations return400 Bad Request, not 409.
Option B is invalid because Kafka Connect does not have a strict concept of "capacity" that prevents connector creation with a 409.
Reference:Apache Kafka Connect REST API documentation

Seehttps://docs.confluent.io/current/streams/developer-guide/dsl-api.html#joining

Increase linger.ms
Explanation:
batch.size controls how many bytes of data to collect before sending messages to the Kafka broker. Set this as high as possible, without exceeding available memory. Enabling compression can also help make more compact batches and increase the throughput of your producer. Linger.ms will have no effect as the batches are already full