Series · 2 posts
A two-part deep dive into what makes Kafka fast — from sequential I/O and zero-copy to partitions and consumer groups.
Kafka's speed comes from two counterintuitive design choices: deliberately writing to disk (not memory) but using sequential I/O, and Zero-Copy to move data from disk to NIC without CPU involvement.
Kafka's horizontal scalability comes from partition design: each partition is an independent log, Consumer Groups enable parallel consumption, and replication provides durability without a large performance penalty.