Apache Kafka
maang.io System Design Series
Apache Kafka is not a queue but a distributed commit log: topics split into ordered, replicated partitions of immutable, offset-addressed records. Producers append, consumer groups read at their own pace, and retention keeps messages replayable. Master partitions, the in-sync-replica set, log segments, and exactly-once semantics, and you understand the backbone of modern event-driven and streaming systems.
This deep dive comes in four parts:
- Foundations & Core Concepts — topics, partitions, offsets, and consumer groups.
- Internals — brokers, leaders/ISR, the high-watermark, log segments, and retention, with worked numbers.
- Advanced Internals — the idempotent producer, transactions/exactly-once, and KRaft.
- Interview — Staff/Principal Q&A: ordering, delivery guarantees, and capacity reasoning.