Skip to main content

​
Overview

The Resume Generator uses MongoDB for data persistence. This guide helps you resolve common MongoDB connection issues, particularly with MongoDB Atlas.

​
Connection Configuration

The database connection is handled in backend/src/config/database.js:5-15 and initialized in backend/server.js:5.
The application uses Mongoose to connect to MongoDB with the connection string from the MONGO_URI environment variable.

​
Common Connection Errors

Cause: MongoDB server is unreachable. Common reasons include:
  • Incorrect connection string
  • IP not whitelisted in MongoDB Atlas
  • Network connectivity issues
  • Firewall blocking connection
Solutions:

​
1. Verify Connection String

Check your backend/.env file:
MONGO_URI=mongodb+srv://username:[email protected]/database?retryWrites=true&w=majority
Common mistakes:
  • Missing protocol (mongodb+srv://)
  • Incorrect cluster URL
  • Missing database name
  • Special characters in password not URL-encoded

​
2. Whitelist Your IP Address (MongoDB Atlas)

Most common issue: Your IP address is not whitelisted in MongoDB Atlas.
Steps:
  1. Go to MongoDB Atlas
  2. Select your project
  3. Navigate to Network Access (left sidebar)
  4. Click IP Access List
  5. Click Add IP Address
  6. Options:
    • Add Current IP Address (for your current IP)
    • Allow Access from Anywhere (0.0.0.0/0) - for development only
    • Add specific IP addresses for production
Using 0.0.0.0/0 (anywhere) is convenient for development but not recommended for production as it allows connections from any IP address.

​
3. Check Cluster Status

  • Ensure your MongoDB Atlas cluster is running (not paused)
  • Free tier clusters pause after inactivity
  • Resume the cluster from the Atlas dashboard if paused

​
4. Test Connection

After whitelisting, restart your backend:
cd backend
npm run dev
You should see: "Connected to Database"
Error Message: "bad auth: Authentication failed"Cause: Incorrect database username or password.Solutions:

​
1. Verify Database User Credentials

  1. Go to MongoDB Atlas → Database Access
  2. Check your database username exists
  3. If password is incorrect, edit the user and reset password

​
2. Update Connection String

In backend/.env:
MONGO_URI=mongodb+srv://YOUR_USERNAME:[email protected]/database
Replace:
  • YOUR_USERNAME with your database username (not your Atlas login email)
  • YOUR_PASSWORD with your database password

​
3. URL-Encode Special Characters

If your password contains special characters, they must be URL-encoded:
CharacterEncoded
@%40
:%3A
/%2F
?%3F
#%23
&%26
Example:
  • Password: P@ssw0rd!
  • Encoded: P%40ssw0rd!
Or use Node.js to encode:
encodeURIComponent('P@ssw0rd!')

​
4. Restart Backend

cd backend
npm run dev
Cause: The MONGO_URI format is incorrect.Solutions:

​
Correct Format for MongoDB Atlas:

MONGO_URI=mongodb+srv://<username>:<password>@<cluster>.mongodb.net/<database>?retryWrites=true&w=majority

​
Components:

  • Protocol: mongodb+srv:// (for Atlas) or mongodb:// (for local)
  • Username: Your database user
  • Password: URL-encoded password
  • Cluster: Your cluster hostname (e.g., cluster0.abc123.mongodb.net)
  • Database: Your database name (optional, defaults to test)
  • Options: Query parameters for connection settings

​
Get Connection String from Atlas:

  1. Go to MongoDB Atlas → Database
  2. Click Connect on your cluster
  3. Choose Connect your application
  4. Copy the connection string
  5. Replace <password> with your actual password
  6. Replace <database> with your database name (or use test)

​
Common Mistakes:

  • Missing :// after protocol
  • Spaces in the connection string
  • Quotes around the connection string in .env file (not needed)
  • Using MongoDB Compass connection string instead of application string
Symptom: Backend logs show undefined for process.env.MONGO_URICause: .env file is missing, in wrong location, or not loaded.Solutions:

​
1. Verify .env File Location

The .env file must be in the backend/ directory:
project-root/
├── backend/
│   ├── .env          ← Should be here
│   ├── server.js
│   └── package.json
└── frontend/

​
2. Check .env File Contents

backend/.env should contain:
MONGO_URI=mongodb+srv://username:[email protected]/database
JWT_SECRET=your_jwt_secret
GOOGLE_GENAI_API_KEY=your_gemini_api_key

​
3. Verify dotenv is Loaded

Check backend/server.js:1 contains:
require("dotenv").config()

​
4. Restart Backend

Environment variables are loaded at startup:
cd backend
npm run dev
If you change .env values, you must restart the backend server for changes to take effect.
Error: "Server selection timed out after 30000 ms"Cause: Cannot reach MongoDB server within timeout period.Solutions:

​
1. Check Internet Connection

  • Ensure you have active internet connection
  • Test connectivity: ping cluster0.abc123.mongodb.net

​
2. Verify Firewall Settings

  • Corporate/university firewalls may block MongoDB ports (27017)
  • Try from a different network
  • Contact network administrator if on restricted network

​
3. Check VPN

  • Some VPNs block database connections
  • Try disconnecting VPN or whitelisting VPN IP in Atlas

​
4. Verify Cluster Region

  • Choose cluster region closest to your location for better latency
  • Check Atlas dashboard for cluster status

​
Local MongoDB Setup

If you prefer using a local MongoDB instance instead of Atlas:

​
1. Install MongoDB Locally

# macOS
brew install mongodb-community

# Ubuntu/Debian
sudo apt-get install mongodb

# Windows
# Download from https://www.mongodb.com/try/download/community

​
2. Start MongoDB Service

# macOS
brew services start mongodb-community

# Linux
sudo systemctl start mongodb

# Windows
# MongoDB runs as a service after installation

​
3. Update Connection String

backend/.env: 
MONGO_URI=mongodb://localhost:27017/resume-generator

​
4. Verify Connection

# Test connection
mongo
# or
mongosh

​
Database Connection Best Practices

Security

  • Use strong passwords for database users
  • Whitelist only necessary IP addresses
  • Never commit .env files to version control
  • Rotate credentials if exposed

Performance

  • Choose cluster region near your application
  • Use connection pooling (handled by Mongoose)
  • Monitor connection errors in production
  • Set appropriate timeout values

​
Verification Checklist

Before seeking further help, verify:
  • .env file exists in backend/ directory
  • MONGO_URI is correctly formatted
  • Database username and password are correct
  • Special characters in password are URL-encoded
  • Your IP is whitelisted in MongoDB Atlas Network Access
  • MongoDB Atlas cluster is running (not paused)
  • Backend server is restarted after changing .env
  • You see “Connected to Database” in console

​
Additional Resources

Common Issues

General troubleshooting for JWT, file uploads, and more

MongoDB Atlas Docs

Official MongoDB Atlas documentation

Build docs developers (and LLMs) love

Get started for freeTalk to us