# MongoDB - NOSQL Database
MongoDB is a **document-oriented NoSQL database** used for high-volume data storage. Instead of using tables and rows as in relational databases, MongoDB uses **collections and documents**.
### **Key Features of MongoDB**
1. **Schema-less** – No fixed structure, allowing flexibility.
2. **Scalability** – Horizontally scalable using **sharding**.
3. **High Performance** – Fast read and write operations.
4. **Replication** – Provides **high availability** using replica sets.
5. **Indexing** – Supports different types of indexes to improve query performance.
6. **Aggregation Framework** – Enables complex data transformations.
### **MongoDB Architecture**
MongoDB follows a **distributed architecture** with multiple components:
1. **Client** – Applications interact with MongoDB using drivers.
2. **MongoDB Server** – Stores and manages the data.
3. **Replica Set** – Ensures **fault tolerance** and high availability.
4. **Sharded Cluster** – Enables horizontal scaling for large datasets.
5. **Config Servers** – Store metadata for sharded clusters.
6. **Mongos Router** – Distributes queries across shards.
### **Basic MongoDB Operations**
**1. Creating a Database**
```javascript
use myDatabase;
```
2. Creating a Collection
```javascript
db.createCollection("users");
```
3. Inserting a Document
```javascript
db.users.insertOne({
name: "John Doe",
email: "john@example.com",
age: 28,
created_at: new Date()
});
```
4. Finding Documents
```javascript
db.users.find({ age: { $gt: 25 } });
```
5. Updating a Document
```javascript
db.users.updateOne(
{ email: "john@example.com" },
{ $set: { age: 30 } }
);
```
6. Deleting a Document
```javascript
db.users.deleteOne({ email: "john@example.com" });
```
### **MongoDB Use Cases**
* **Big Data Applications**
* **Real-time Analytics**
* **Internet of Things (IoT)**
* **Content Management Systems**
* **Mobile and Web Apps**
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