MongoDB — Flexible Document Database
MongoDB stores data as JSON-like documents instead of rows and tables. Each document can have a different structure, making it ideal for evolving schemas, nested data, and applications that don't fit the relational model.
Document vs Row
SQL Row (rigid — all rows must have same columns):
| id | name | email | phone |
| 1 | Alice | alice@email.com | +91-9876543 |
| 2 | Bob | bob@email.com | NULL |
MongoDB Document (flexible — each document can differ):
{
"_id": "507f1f77bcf86cd799439011",
"name": "Alice",
"email": "alice@example.com",
"phone": "+91-9876543",
"address": { ← Nested object (no JOIN needed)
"city": "Bangalore",
"state": "Karnataka"
},
"tags": ["admin", "developer"], ← Arrays built-in
"preferences": {
"theme": "dark",
"notifications": true
}
}
When to Use MongoDB
Good fit:
•Product catalogs (each product has different attributes)
•User profiles (flexible preferences, nested data)
•Content management (blog posts, articles, mixed media)
•Event logs and activity feeds
•Real-time analytics with complex nested queries
•Rapid prototyping where schema changes frequently
Not a good fit:
•Financial transactions (need ACID across multiple documents)
•Complex relationships with many-to-many joins
•Reporting with ad-hoc aggregations across many fields
•When your data is naturally tabular and structured
Quick Start
javascript
// Connect
const { MongoClient } = require('mongodb');
const client = new MongoClient('mongodb://localhost:27017');
await client.connect();
const db = client.db('myapp');
const users = db.collection('users');
// Insert
await users.insertOne({ name: 'Alice', email: 'alice@example.com', age: 30 });
await users.insertMany([
{ name: 'Bob', email: 'bob@example.com', age: 25 },
{ name: 'Charlie', email: 'charlie@example.com', age: 35 }
]);
// Find
const user = await users.findOne({ email: 'alice@example.com' });
const all = await users.find({ age: { $gte: 25 } }).toArray();
// Update
await users.updateOne({ email: 'alice@example.com' }, { $set: { age: 31 } });
// Delete
await users.deleteOne({ email: 'bob@example.com' });
