Points 1 & 2. There is no direct communication between a producer and consumer. The producer writes to the broker, the consumer reads from the broker. There is

Points 1 & 2. There is no direct communication between a producer and consumer. The producer writes to the broker, the consumer reads from the broker. There is a detailed flow diagram for the producer side operations in the article, and this deck has more of the details of how both the producer and consumer work: https://www.slideshare.net/apurva2/introducing-exactly-once-semantics-to-apache-kafka https://www.slideshare.net/apurva2/introducing-exactly-once-... 3. Yes, it has been tested empirically. Quoting from the article: > We wrote over 15,000 LOC of tests, including distributed > tests running with real failures under load and ran them > every night for several weeks looking for problems. This > uncovered all manner of issues, ranging from basic > coding mistakes to esoteric NTP synchronization issues > in our test harness. A subset of these were distributed > chaos tests, where we bring up a full Kafka cluster with > multiple transactional clients, produce message > transactionally, read these messages concurrently, and > hard kill clients and servers during the process to > ensure that data is neither lost nor duplicated.