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Data & Analytics · Intermediate

Apache Cassandra

An open-source, masterless, distributed wide-column database designed for high write throughput and multi-datacenter availability.

Definition

Cassandra uses consistent hashing on the partition key, a peer-to-peer ring, and tunable consistency per query (ONE, QUORUM, ALL). CQL looks like SQL but has no joins, and tables are modeled around queries. Amazon Keyspaces and the Cosmos DB for Apache Cassandra API are compatible managed services.

Example

SELECT * FROM readings WHERE sensor_id = 'S1' AND day = '2026-11-01';

Exam tip

Cassandra is modeled query-first: you design one table per query pattern.

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