Installation & Atlas Setup

You can run MongoDB in two ways:

  1. MongoDB Atlas: Fully managed cloud service (Recommended for beginners & production).
  2. Local / Docker: Self-hosted on your machine.

1. MongoDB Atlas (Free Cloud Tier)

The easiest way to start is using the free tier on Atlas.

  1. Sign Up: Go to MongoDB Atlas and create an account.
  2. Create Cluster: Select Build a Database → M0 Sandbox (Free) → Select a region close to you → Create.
  3. Security Setup:
    • Database User: Create a username (e.g., admin) and a strong password. Save this password!
    • Network Access: Add your current IP address (or 0.0.0.0/0 to allow all, but be careful).
  4. Connect: Click Connect → Drivers to get your connection string.

2. Local Installation via Docker

If you prefer running locally, Docker is the cleanest method.

Quick Start (One-Liner)

docker run -d \
  --name mongodb \
  -p 27017:27017 \
  -e MONGO_INITDB_ROOT_USERNAME=admin \
  -e MONGO_INITDB_ROOT_PASSWORD=password123 \
  mongo:latest

Production-Ready docker-compose.yml

This setup includes Mongo Express, a web-based admin interface.

version: '3.8'
services:
  mongodb:
    image: mongo:latest
    container_name: mongodb
    ports:
      - "27017:27017"
    environment:
      MONGO_INITDB_ROOT_USERNAME: admin
      MONGO_INITDB_ROOT_PASSWORD: password123
    volumes:
      - mongo-data:/data/db
    restart: unless-stopped

  mongo-express:
    image: mongo-express
    container_name: mongo-express
    ports:
      - "8081:8081"
    environment:
      ME_CONFIG_MONGODB_ADMINUSERNAME: admin
      ME_CONFIG_MONGODB_ADMINPASSWORD: password123
      ME_CONFIG_MONGODB_URL: mongodb://admin:password123@mongodb:27017/
    depends_on:
      - mongodb
    restart: unless-stopped

volumes:
  mongo-data:

Run with docker-compose up -d and visit http://localhost:8081.

3. The Connection String

The Connection String is the URL your application uses to find and authenticate with the database.

Interactive: Connection String Builder

Construct a valid URI by adjusting the parameters below.

Generated Connection String
mongodb://admin:password123@localhost:27017/?retryWrites=true&w=majority

Connection Options Explained

Why add ?w=majority?

  • w=majority (Write Concern): This ensures that a write is acknowledged by the majority of nodes in the Replica Set (e.g., 2 out of 3) before returning success to the application. This prevents data loss if the Primary crashes immediately after a write.
  • retryWrites=true: If a network glitch occurs during a write, the driver will automatically retry the operation once.
  • readPreference: Controls where your app reads from.
  • primary: (Default) Always read from Primary (Strong Consistency).
  • secondaryPreferred: Read from Secondary if available (Eventual Consistency, better performance).

4. Verification

Once your database is running, verify the connection using mongosh (MongoDB Shell) or a GUI like Compass.

# Connect to local
mongosh "mongodb://admin:password123@localhost:27017/"

# Expected Output
# Current Mongosh Log ID: ...
# Connecting to: mongodb://admin:password123@localhost:27017/
# ...
# test>