🧱

Apache Cassandra

Apache Cassandra is a free, open-source wide-column NoSQL database originally built at Facebook and now maintained by the Apache Software Foundation. It ranks #22 in real-world usage at roughly 2.9% adoption, and it's chosen when data volume outgrows what a single server can hold — it spreads writes across many machines with no single point of failure.

📝 Quick facts
Type: Wide-column database (NoSQL, distributed)
Made by: Apache Software Foundation (originated at Facebook)
License: Free, open-source (Apache 2.0)
Hosting: Self-hosted or cloud-managed (e.g. DataStax Astra, AWS Keyspaces)
Primary use case: Massive write-heavy workloads distributed across many servers

Jump to: Example (CQL)Getting started Best for

Example (CQL)

Cassandra Query Language (CQL) looks SQL-like, but tables are designed around how you'll query them, not around normalized relationships.

CREATE TABLE users_by_email (
  email text PRIMARY KEY,
  user_id uuid,
  name text
);

INSERT INTO users_by_email (email, user_id, name)
VALUES ('[email protected]', uuid(), 'Ada');

SELECT * FROM users_by_email WHERE email = '[email protected]'; -- fast lookup by partition key

Getting started

The fastest way to try Cassandra locally is with Docker, then connect using its interactive shell, cqlsh.

# run a single-node cluster locally
docker run --name cassandra -p 9042:9042 -d cassandra:latest

# connect with the CQL shell
docker exec -it cassandra cqlsh

🎯 Best for — applications with huge, ever-growing write volume that must stay online across data centers, like messaging platforms, IoT telemetry, and large-scale event logging.