NoSQL
Databases that don't use traditional table-based relational models. Includes document stores, key-value, graph, and column-family databases.
What is NoSQL?
Databases that don't use traditional table-based relational models. Includes document stores, key-value, graph, and column-family databases.
NoSQL is a foundational concept that sits in the Database Fundamentals area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "NoSQL" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn NoSQL in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the NoSQL lessonRelated lessons
Lessons that touch on NoSQL as part of a larger topic.
SQL vs NoSQL
Database model comparison, relational vs non-relational data stores
foundation · core fundamentals
Document Stores
Databases that think in JSON, flexible schemas for modern applications
intermediate · database types storage
Column-Family Stores
Wide-column databases like Cassandra and HBase, built for massive scale with flexible schemas
intermediate · database types storage
LSM Trees
The write-optimized data structure behind Cassandra, RocksDB, LevelDB, and most modern NoSQL databases
intermediate · database types storage
NewSQL Databases
Distributed SQL databases that promise the scalability of NoSQL with the ACID guarantees of traditional SQL. CockroachDB, Google Spanner, and the NewSQL movement
intermediate · database types storage
See also
Related glossary terms you might want to look up next.
SQL
Structured Query Language for managing relational databases. Tables, rows, columns, and powerful joins to query related data.
Database
An organized collection of data that can be easily accessed, managed, and updated. The backbone of almost every application.
BASE
An alternative to ACID for distributed systems: Basically Available, Soft state, Eventually consistent. Trades strong consistency for availability.