How much data does kafka send to a consumer?

let's say i have a data source that send data to the kafka cluster, the msgs are stored in a kafka topic (with one partition to simplify) and waiting to be consumed, a consumer in the other side (spark for example) is set to receive that data, my question is how much data kafka will deliver to spark**?**

i know that we can configure spark to listen to kafka for a defined amount of time and hence receive X amount of data , but i want to understand the kafka's perspective, how much data will kafka deliver in one push, can we configure it ? can we for example make sure that kafka send only one msg (the exact msg that has been received from tha data source, it could be one row of a table for example)?

The short answer is yes you can control the number of records via a combination of the below kafka consumer configs:

max.poll.records
fetch.max.bytes fetch.min.bytes max.partition.fetch.bytes max.poll.interval.ms

Kafka consumer model is built on a poll model, where the consumer is the one responsible to issue the polling action every specific internal, and all the configuration related to the bytes transferred, records count, time to poll, session management and much more configuraiton are on the consumer side, and that is one of the biggest advantages of Kafka architecture, that is totally free from being dependent on the number of consumers dealing with it.

I highly recommend reading more about kafka consumer model, here is a good starter

you can check the kafka-consumer configs here