How to Choose a Database?

#architecture #beginners #database #systemdesign

Before choosing a database, we must understand the types of databases that exist.

1.Relational Databases (1970s)
In 1970, Edgar F. Codd proposed storing data in tables (relations) and treating them using mathematical principles.
This led to the creation of Relational Databases.
They offer:

Atomicity
Consistency
Isolation
Durability (ACID properties)

Examples include:

MySQL
PostgreSQL

Relational databases are powerful when data is structured and transactional consistency is critical.
However, as systems scale and joins grow across millions of rows, performance tuning and horizontal scaling become challenging.

2.Key–Value Databases (2000s Scaling Era)
In the 2000s, companies like Amazon faced massive scalability challenges.
Instead of complex relational joins, they proposed storing data as:
Key → Value

For example:
UserID → List of Orders

A popular example is: Redis

Key–Value databases offer:

Extremely fast lookups
Easy horizontal scaling
Great performance for caching and session storage However, they are not ideal for handling complex relationships between data.

3. Graph Databases
Graph databases store data as:
Nodes
Edges (relationships)
Example: Neo4j

They are extremely useful when relationships are first-class citizens, such as:

Social networks
Recommendation systems
Fraud detection Graph databases shine when traversing connected data efficiently.

4.Document Databases:
Document database stores data as JSON-like documents

Example: MongoDb

Document Databases offer:
-Easy Horizontal Scaling
-Flexible Schema
-Better support for hierarchical data

While modern document databases support limited joins and aggregations, they are not as optimized for complex relational queries as relational databases.

Final Verdict
Don’t choose a database by default.
Choose a database based on how you access and scale your data.

If you need: