Kafka, From Zero

The distributed log everyone runs in production: topics, partitions, offsets, and consumer groups — append-only streams you can replay, not a traditional queue.

1. It's a Log, Not a Queue Kafka is a durable, append-only log split into partitions; consumers track their own position with offsets and reading never deletes anything, which is why one stream can feed many readers and be replayed.
2. Producing and Consuming for Real The everyday loop: producers pick a partition by key, consumer groups split partitions among members for parallelism, and committing offsets is how you remember what you've processed.
3. Production Reality Delivery guarantees and why duplicates happen, building idempotent consumers, surviving rebalances, how retention quietly deletes old data, and when Kafka is the wrong tool.