Big Data & Hadoop · Module 7 of 10

NoSQL for big data

Store massive, fast-changing data with NoSQL databases.

📖 Key ideas

Key-value (Redis, DynamoDB), document (MongoDB), wide-column (HBase, Cassandra), graph (Neo4j).
Designed to scale horizontally.
CAP theorem: consistency, availability, partition tolerance trade-offs.
Cassandra handles huge write volumes across data centres.
Choose based on access patterns.

💡 Real-life example: NoSQL databases are specialised storage rooms: cold store, wardrobe, library, each fits different items.

Wide-column storeRows with flexible columns at scale

CAP theoremTrade-off between consistency and availability under partitions

CassandraDistributed wide-column database

Eventual consistencyReplicas agree over time