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Farhad Rahimi Klie
Farhad Rahimi Klie

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A Complete Guide to MongoDB for Developers (With Code Examples)

MongoDB has become one of the most popular NoSQL databases in the world. Its flexible schema, JSON-like documents, and developer-friendly ecosystem make it a top choice for modern applications, from small side projects to large-scale enterprise systems.

In this article, you will learn everything you need to know to get started with MongoDB, from installation to CRUD operations, indexes, aggregation, schema design, and best practices.

1. What Is MongoDB?

MongoDB is a NoSQL document database that stores data in BSON (Binary JSON) format. Unlike relational databases, MongoDB does not require predefined schemas, making it more flexible for fast-moving projects and distributed systems.

Key MongoDB Features

  • Schema-less documents
  • Horizontal scaling + sharding
  • High availability with replica sets
  • Rich query language
  • Aggregation framework
  • Integrated indexing
  • Great performance for read/write-heavy applications

2. MongoDB Architecture Overview

MongoDB stores data using the following hierarchy:

MongoDB
 └── Database
      └── Collection
            └── Document
                  └── Field (key/value)
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Example:

myDatabase
 └── users (collection)
        └── { name: "Klie", age: 22 } (document)
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3. Installing & Connecting to MongoDB

Install MongoDB on your system

You can install MongoDB Community Edition using:

  • Windows: MSI Installer
  • macOS: brew install mongodb-community
  • Linux: Official MongoDB repository

Connect using the Mongo Shell 

mongosh
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Connect in Node.js (using Mongoose) 

import mongoose from "mongoose";

mongoose.connect("mongodb://localhost:27017/mydb")
  .then(() => console.log("MongoDB connected"))
  .catch(err => console.log(err));
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4. Basic MongoDB Commands

Show all Databases 

show dbs
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Create/Use Database 

use myDatabase
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Show Collections 

show collections
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5. Creating a Collection & Inserting Documents

Insert One Document 

db.users.insertOne({
  name: "Klie",
  age: 24,
  skills: ["C++", "Node.js", "MongoDB"]
});
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Insert Many Documents 

db.users.insertMany([
  { name: "Farhad", age: 22 },
  { name: "Rahimi", age: 30 }
]);
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6. Querying Documents

Find All 

db.users.find();
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Find with Conditions 

db.users.find({ age: { $gt: 20 } });
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Find One 

db.users.findOne({ name: "Klie" });
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7. Updating Documents

Update One 

db.users.updateOne(
  { name: "Klie" },
  { $set: { age: 25 } }
);
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Update Many 

db.users.updateMany(
  { age: { $lt: 30 } },
  { $set: { status: "active" } }
);
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8. Deleting Documents

Delete One 

db.users.deleteOne({ name: "Farhad" });
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Delete Many 

db.users.deleteMany({ age: { $gt: 40 } });
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9. Indexing in MongoDB

Indexes help improve query performance.

Create Index 

db.users.createIndex({ name: 1 });  // 1 = ascending
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List Indexes 

db.users.getIndexes();
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Drop Index 

db.users.dropIndex("name_1");
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10. The Aggregation Framework

Aggregation is like SQL’s GROUP BY.

Example: Group by age and count users 

db.users.aggregate([
  { $group: { _id: "$age", total: { $sum: 1 } } }
]);
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Example: Sort by age 

db.users.aggregate([
  { $sort: { age: 1 } }
]);
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Example: Match + Sort + Limit 

db.users.aggregate([
  { $match: { age: { $gt: 20 } } },
  { $sort: { age: -1 } },
  { $limit: 5 }
]);
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11. Mongoose (Node.js ODM) Example

User Model 

import mongoose from "mongoose";

const userSchema = new mongoose.Schema({
  name: String,
  age: Number,
  skills: [String]
});

const User = mongoose.model("User", userSchema);

export default User;
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Create a User 

const user = await User.create({
  name: "Klie",
  age: 24,
  skills: ["C++", "Node.js"]
});
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Find Users 

const users = await User.find({ age: { $gt: 20 } });
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12. Schema Design Best Practices

Document-Oriented Mindset

Think in objects, not tables.

Embed when:

  • Data reads together
  • Many-to-one or one-to-few
  • Example: user + address

Reference when:

  • One-to-many with large counts
  • Example: user → 1,000 posts

Avoid deeply nested documents

Keep document size < 16MB.

13. Security Best Practices

  • Always use authentication (mongod --auth)
  • Use environment variables for connection strings
  • Enable role-based access control
  • Use TLS/SSL for production
  • Restrict access with IP whitelisting

14. MongoDB Use Cases

MongoDB is used in:

  • Real-time dashboards
  • E-commerce catalogs
  • Social media apps
  • Mobile backends
  • IoT applications
  • Logging systems
  • Content management platforms

15. Conclusion

MongoDB is a powerful, flexible, and highly scalable NoSQL database that fits modern development workflows very well. Whether you are building an e-commerce platform, a social media system, or a personal project, MongoDB offers simplicity and strong performance.

If you are working with JavaScript, Node.js, or full-stack applications, MongoDB integrates seamlessly and accelerates development time.

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