Databases: SQL vs NoSQL

Choosing a database is the most critical decision in system design. Do you want strict order or total flexibility?

Think: Excel Sheets. Data is stored in strict tables with Rows and Columns. Tables are linked (Joined) by IDs.

Examples: PostgreSQL, MySQL, SQL Server

Think: JSON Files. Data is stored as flexible documents. One user can have 3 fields, the next can have 50. No rules.

Examples: MongoDB, DynamoDB, Firestore

🕹️ The "Schema Enforcer" Game

Mission: Try to save a "User" object that has an unexpected new field: "hobby": "Chess".

SQL DB Strict Schema

Incoming Data

{
  "id": 1,
  "name": "Alice",
  "hobby": "Chess" // Unexpected!
}

Schema: id (INT), name (VARCHAR)

id	name
1	Alice

Waiting...

NoSQL DB Flexible Schema

Incoming Data

{
  "id": 2,
  "name": "Bob",
  "hobby": "Gaming" // New field? OK!
}

Collection: Users
(Accepts Anything)

{ "id": 2, "name": "Bob", "hobby": "Gaming" }

Waiting...