NoSQL (Not Only SQL) databases are non-relational databases designed to handle large-scale data storage and high-speed operations. Unlike traditional SQL (relational) databases, NoSQL databases do not use structured tables, rows, and columns. Instead, they support flexible schema models such as key-value pairs, documents, column-family stores, and graph structures.

Why use it?

  • Handles big data and high-velocity applications
  • Schema-less (flexible structure)
  • Horizontally scalable (distributed across multiple servers)
  • Designed for high availability and fault tolerance
  • Supports unstructured and Semi-Structured Data

Challenges of using it

  • No Standard Query Language: Each database has its own querying method
  • Limited ACID Transactions: Some NoSQL databases sacrifice consistency for speed
  • Data Redundancy: NoSQL allows denormalization, which can lead to redundant data

See also NoSQL Database Model Comparison.