In this section, we'll explore the world beyond traditional relational databases. NoSQL (Not Only SQL) databases represent a paradigm shift in how we store, manage, and retrieve data.

Four main types of NoSQL databases

Key Concepts

• Schema Flexibility: Unlike relational databases, NoSQL databases often allow for dynamic schemas, enabling documents in the same collection to have different fields.
• Horizontal Scalability: Designed to expand seamlessly across multiple servers.
• Distribution Models: Often built with distributed architectures in mind.
• CAP Theorem: Understanding the trade-offs between Consistency, Availability, and Partition tolerance.

Main Types of NoSQL Databases

1. Document Stores (e.g., MongoDB, Couchbase)

   • Store data in document formats like JSON, BSON, or XML
   • Ideal for content management systems and e-commerce platforms

2. Key-Value Stores (e.g., Redis, DynamoDB)

   • Simple data storage using unique keys
   • Perfect for caching and session management

3. Column-Family Stores (e.g., Cassandra, HBase)

   • Store data in column families
   • Excel in time-series data, weather data, and IoT applications

4. Graph Databases (e.g., Neo4j, Amazon Neptune)

   • Represent data as nodes, edges, and properties
   • Excellent for social networks and recommendation engines