Common Mistakes to Avoid When Working with the MERN Stack

The MERN stack is one of the widely used JavaScript tech stacks out there. It combines MongoDB, Express.js, React, and Node.js to enable the development of full-stack applications for developers with ease. It’s fast, scalable, and efficient—if you know how to make use of it. Several developers, especially the ones starting their journey, fall into the common pitfalls when working with the MERN stack. And trust me, these mistakes can cost you hours of frustration.

Let’s dive into the most common mistakes to avoid when working with the MERN stack for custom software development, so you can save time and build better apps.

1. Skipping JavaScript Basics

This is a very common mistake. A lot of developers jump straight into React or Node.js tutorials without comprehending the fundamentals of Javascript. You should keep in mind that Javascript is used to build MERN Stack. If you don’t understand callbacks, promises, async/await, or closures, you’ll find yourself stuck all the time.

Take your time to completely understand and master the concepts of ES6+ features like arrow functions, destructuring, template literals, and modules. In addition to it, ensure that the concepts of how JavaScript handles asynchronous operations are clear so that working with API calls and MongoDB queries becomes easy.

So, don’t skip the foundations. Build your skills from the ground up.

2. Not Managing Errors Properly

No denying errors happen. As a developer what is important is tackling them. A big mistake in MERN apps is avoiding proper error handling—especially on the backend.

For example, if one of the MongoDB queries fails and the error is not caught, your server could crash. The same goes for React—if an APi response is not handled, your UI will go into vain.

Here’s a simple example of proper error handling in Express:

javascript

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app.get('/api/data', async (req, res) => {

try {

const data = await fetchData();

res.status(200).json(data);

} catch (error) {

console.error(error);

res.status(500).json({ message: 'Server Error' });

}

});

Also, consider using error boundaries in React to catch rendering errors.

3. Ignoring State Management in React

In the beginning, using useState for everything can work fine. But once your app grows, proper management of the state gets tricky. Without careful consideration, the components become complex for debugging because of the tangles.

Many developers avoid using proper state management tools like Redux, Context API, or even React Query. As a result, at the end they have to duplicate the logic across components and developers just pass props through the layers.

Here’s the deal—simple state logic is fine for smaller and simple apps, whereas we recommend using global state for larger applications. It helps you stay organized and makes data flow predictable.

4. Poor Deployment

After building your app, deploying it correctly is as significant—and a lot of developers mess it up. Whether you're using Heroku, Vercel, Render, or a VPS, a few common mistakes while deployment leads to inadequate app performance and downtime.

Some of these include:

• Forgetting to set environment variables in production

• Not building the React app before deployment

• Serving the frontend and backend separately without configuring proxies

• Not handling CORS in production

Make sure that the build is tested before deployment. For full-stack MERN apps, the best practice is to host the frontend (React) and backend (Node/Express) together. Use express.static() to serve the React build from your backend:

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app.use(express.static(path.join(__dirname, 'client/build')));

Also, check the environment variables and API endpoints twice to avoid last moment errors. What works in development may not work in production without proper configuration.

5. Using Too Many Third-Party Libraries Without Understanding Them

We all love packages that make development easier. But one big trap MERN developers fall into is relying too heavily on third-party libraries without understanding how they work. It’s like building a house using tools you’ve never used before—something is bound to break.

Using a package like axios, mongoose, or redux is great, but before you install any library, ask yourself:

• Do I really need this?

• Can I solve this problem with plain JavaScript?

• Is this package well-maintained?

Also, make sure to read the documentation and understand how the package works before using it in your project. Blindly copying and pasting code from Stack Overflow or GitHub without knowing what it does can create hidden bugs or performance issues.

Stick to a few trusted libraries, and take the time to master them. Less is often more in the long run.

6. Forgetting to Secure the Application

Security often takes a back seat during development. But leaving your app open to attacks is a dangerous game. Many developers forget to implement key security practices in their MERN apps.

Here are some common security oversights:

• Not validating user input

• Exposing sensitive data in the client

• Forgetting to hash passwords before storing them

• Not using environment variables for API keys

• Leaving your MongoDB connection open without IP whitelisting

To fix this, use tools like dotenv to manage your environment variables. Also, always sanitize and validate user inputs using packages like express-validator or Joi. And don’t forget to hash passwords using bcrypt.

7. Poor Project Structure

When you're working on a MERN stack project, it's easy to dump everything into a single folder, especially during the early stages. But this quickly leads to messy, unmanageable code.

A common mistake is not separating concerns. For instance, mixing up React component logic with API calls or having all your routes, controllers, and models in one file.

Here’s a cleaner structure to consider:

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client/

├── public/

├── src/

├── components/

├── pages/

├── services/

├── App.js

└── index.js

server/

├── controllers/

├── models/

├── routes/

├── config/

└── server.js

This setup keeps things organized and easier to debug or scale.

Conclusion

Working with the MERN stack is exciting and powerful—but only if you avoid the common traps. From skipping JavaScript basics to poor project structure, weak security, or bad deployment habits, these mistakes can derail even the best ideas.

The good news? Now that you know what to watch out for, you're already ahead of the curve. Keep learning, stay curious, and build smarter. The MERN stack offers endless potential—use it wisely!

FAQs

1. What is the MERN stack best used for? The MERN stack is perfect for building full-stack web applications, especially SPAs (Single Page Applications) like dashboards, eCommerce platforms, social media apps, and more.

2. Can I learn the MERN stack without knowing JavaScript? Technically yes, but it’s not recommended. JavaScript is the backbone of all MERN stack technologies, so understanding it is essential.

3. Is Redux required in every MERN project? Nope. For small apps, React’s built-in state management is enough. Redux or Context API is better for larger projects with complex state needs.

4. What’s the best way to connect React with Node.js? Use API endpoints in your Express backend and fetch them using fetch() or axios in React. Configure proxy settings in development to avoid CORS issues.

5. Do I need to use MongoDB, or can I use another database with MERN? MERN is specifically built around MongoDB. However, if you prefer another database, like PostgreSQL, you’d be working with a slightly different stack (like PERN).