Deployment Overview

Deploying MERN means running frontend, backend, and database in production.

Local development is not enough.

Common deployment shapes

Separate frontend and backend

React hosted on static hosting/CDN
Express API hosted on server/platform
MongoDB hosted on managed database

React calls the API using production API URL.

Same backend serves React

Express API serves React build files
MongoDB hosted separately

This can be simpler for small apps.

Production checklist

• build React,
• set backend env vars,
• set frontend API URL,
• configure CORS,
• connect MongoDB,
• use HTTPS,
• enable logging,
• handle errors safely,
• avoid exposing secrets,
• test auth flow after deployment.

React build

npm run build

This creates static files.

Backend runtime

Backend needs:

• Node version,
• start command,
• environment variables,
• database connection,
• process manager/platform health checks.

Interview answer

MERN deployment requires building the React frontend, running the Express/Node backend, configuring environment variables, connecting to MongoDB, setting CORS correctly, and using HTTPS. The frontend may be hosted separately as static files or served by Express, while MongoDB is usually hosted as a managed database.