Apache Cassandra
maang.io System Design Series
Apache Cassandra is a masterless, wide-column database built for enormous write volume and always-on availability. It marries Dynamo's distribution (a consistent-hashing ring, leaderless replication, tunable consistency) to Bigtable's storage (the LSM-tree engine). No single point of failure, linear scale by adding nodes, and a consistency dial you turn per query — it's the self-managed cousin of DynamoDB and a system-design interview staple.
This deep dive comes in four parts:
- Foundations & Core Concepts — the masterless ring, partition keys, and replication factor.
- Internals — the write path (commit log → memtable → SSTable) and the LSM storage engine, with worked numbers.
- Advanced Internals — the read path, tunable consistency (
R + W > RF), repair, and tombstones. - Interview — Staff/Principal Q&A: data modeling, consistency reasoning, and failure handling.