Producer Default Partitioner and how keys are hashed

 1. By default, your keys are hashed using the "murmuyr2" algorithm.

2. It is most likely prefered to not override the behavior of the partitioner, but it is possible todo so (partitioner.class).

3. The formula is:

targetPartition = Utils.abs(Utils.murmur2(record.key())) % numPartitions;

4. This means that same key will go to the same partition (we already know this), and adding partitions to a topic will completely alter the formuila