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Apache Cassandra

Distributed NoSQL database - linear scalability, no single point of failure, handles massive data volumes

TL;DR

What: A distributed NoSQL database designed for high availability and scalability.

Why: No single point of failure, linear scalability, handles massive data volumes.

Quick Start

Install with Docker:

docker run --name cassandra -p 9042:9042 -d cassandra:latest

Connect:

docker exec -it cassandra cqlsh

Create keyspace and table:

CREATE KEYSPACE myapp WITH replication = {
  'class': 'SimpleStrategy',
  'replication_factor': 1
};

USE myapp;

CREATE TABLE users (
  user_id UUID PRIMARY KEY,
  name TEXT,
  email TEXT,
  created_at TIMESTAMP
);

Cheatsheet

CommandDescription
DESCRIBE KEYSPACES;List keyspaces
USE keyspace;Select keyspace
DESCRIBE TABLES;List tables
DESCRIBE TABLE name;Show table schema
SELECT * FROM table;Query data
INSERT INTO table (...) VALUES (...);Insert data
EXIT;Exit cqlsh

Gotchas

Data modeling (query-first)

-- Design tables based on queries, not relationships
-- Query: Get all posts by user, sorted by time
CREATE TABLE posts_by_user (
  user_id UUID,
  post_id TIMEUUID,
  title TEXT,
  content TEXT,
  PRIMARY KEY (user_id, post_id)
) WITH CLUSTERING ORDER BY (post_id DESC);

CRUD operations

-- Insert
INSERT INTO users (user_id, name, email, created_at)
VALUES (uuid(), 'John', '[email protected]', toTimestamp(now()));

-- Select
SELECT * FROM users WHERE user_id = some-uuid;

-- Update
UPDATE users SET name = 'Johnny'
WHERE user_id = some-uuid;

-- Delete
DELETE FROM users WHERE user_id = some-uuid;

Primary key structure

-- Partition key only
PRIMARY KEY (user_id)

-- Partition key + clustering column
PRIMARY KEY (user_id, created_at)

-- Composite partition key
PRIMARY KEY ((country, city), user_id)

Collections

-- List
emails LIST<TEXT>

-- Set
tags SET<TEXT>

-- Map
properties MAP<TEXT, TEXT>

Next Steps