How to choose Kafka transaction id for several applications, hosted in Kubernetes?
If the consumer starts the transaction (read-process-write) then the transaction id prefix must be the same for all instances of the same app (so that zombie fencing works correctly after a rebalance). The actual transaction id used is <prefix><group>.<topic>.<partition>.
If you have multiple apps, they should have unique prefixes (although if they consume from different topics, they will be unique anyway).
For producer-only transactions, the prefix must be unique in each instance (to prevent kafka fencing the producers).