When should I use NoSQL instead of SQL?

Use NoSQL for large-scale, flexible, or rapidly changing data; use SQL when you need strong consistency and complex relationships between structured data.

What are the main types of NoSQL databases?

The four main types are document (MongoDB), key-value (Redis), column-family (Cassandra), and graph (Neo4j) databases.

Intermediate🖼️ 20 slides⏱ 4 minDatabases

🗄️ NoSQL Databases

NoSQL databases store data in flexible, non-relational ways and scale horizontally. This visual guide covers document, key-value, column-family, and graph databases, the CAP theorem, and when to choose NoSQL over SQL.

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What Is NoSQL?

Databases that store data in flexible, non-relational ways.

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SQL vs NoSQL

SQL is structured tables; NoSQL is flexible schemas.

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Why NoSQL?

Scale, flexibility, and speed for big or changing data.

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Four Main Types

Document, key-value, column, and graph.

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Document Databases

Store JSON-like documents (MongoDB).

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Key-Value Stores

Simple, fast lookups (Redis).

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Column-Family Stores

Wide columns for big data (Cassandra).

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Graph Databases

Model relationships (Neo4j).

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Flexible Schemas

Add fields without migrations.

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Horizontal Scaling

Spread data across many servers.

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Sharding

Split data to scale writes and storage.

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Replication

Copy data for reliability and reads.

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The CAP Theorem

Trade consistency for availability under partitions.

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Eventual Consistency

Data syncs over time, not instantly.

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Denormalization

Duplicate data for fast reads.

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When to Use NoSQL

Large scale, flexible, fast-changing data.

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When to Use SQL

Strong consistency and complex relations.

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Polyglot Persistence

Use the right database per job.

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Popular NoSQL DBs

MongoDB, Redis, Cassandra, and DynamoDB.

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Getting Started

Model a simple app in a document database.

Frequently Asked Questions

A NoSQL database stores data in flexible, non-relational formats — like documents, key-value pairs, columns, or graphs — and typically scales horizontally.