Kafka documentation <https://www.confluent.io/blog/transactions-apache-kafka/> states:
Finally, in distributed environments, applications will crash or—worse!—temporarily lose connectivity to the rest of the system. Typically, new instances are automatically started to replace the ones which were deemed lost. Through this process, we may have multiple instances processing the same input topics and writing to the same output topics, causing duplicate outputs and violating the exactly once processing semantics. We call this the problem of “zombie instances.” But think about Kafka Stream for example, when different threads, each with its own consumer and producer, actually consume from same topic and write to same topic. Usually when developing processor logic, consume process produce, we actually may want replicas to read from the same topics, but of course different partitions, and write to the same topic. This is how Kafka allows scaling. So in my understanding the zombie problem appears when consumers belonging to the same group are, because of some previous failure e.g. network failure, consuming from the same partition. Am I missing something?
