The MERN stack is one of the well-known web stacks that has acquired significance over other stacks. This is a direct result of its user interface (UI) delivery and execution, cost-efficiency, open-source nature, and ease of switching between customer and server. Its goal is to boost an application's overall performance.

MERN is an easy-to-understand full-stack JavaScript environment that enables the building of dynamic sites and applications. Let’s depict the MERN stack architecture, the four technologies that make it, and how they all work together for a seamless start to finish product.

Table of contents

What is MERN stack?
    ➤  How does the MERN stack work?
    ➤  Is MERN stack front-end or back-end?
Is MERN stack in demand?
MEAN stack vs MERN stack
Business benefits of MERN stack

What is MERN stack?

MERN is the fusion of JavaScript technologies that work hand in hand to enable businesses agility. MERN stack stands for MongoDB, Express, React, and Node - the four technologies that make up the stack.

As we have already covered before:

  • MongoDB is a popular document database;
  • Express is a back-end web application framework for Node.js;
  • React is a client-side JavaScript library;
  • Node.js is a back-end JavaScript runtime environment;

Simply put, the MERN stack is an assortment of strong innovations used to foster adaptable expert software, web, and mobile applications.

How does the MERN stack work?

Below, we have the MERN stack architecture. As we can see, it is made of three parts: a front-end, back-end, and a database - in other words, a full-stack architecture.

Mern stack architecture

The main benefit of MERN is that the whole project can be done using just JavaScript and JSON, so a MERN developer only needs to know one programming language and the JSON document structure.

Let’s break it down by section:


MongoDB: If your application stores any type of data at all - like a social media app that stores user profiles content, comments, likes, and so on, then you are going to need a database. There are many databases to choose from, but MongoDB is the database for MERN.

Any JSON document created in our React front-end can be sent to the Express server where they can be processed and stored directly in MongoDB. It’s important to mention that MongoDB is considered to be a document database, and it was designed to store JSON data natively and technically uses a binary version of JSON called BSON. Everything from its command-line interface to its query language, MongoDB query language (MQL) is built on JSON and JavaScript.

MongoDB also works extremely well with Node.js and makes storing, manipulating and representing JSON data at every tier of your application super easy. The JSON data flows naturally from front-end to back-end, making it fast to build on and reasonably simple to debug.

Why use MongoDB?

  • Flexible data model: MongoDB is a document-oriented database, which means it can store data in flexible JSON-like documents, making it easy to store and access complex, unstructured data.

  • Scalability: MongoDB is designed to scale horizontally across commodity hardware, making it suitable for handling large volumes of data and high-traffic applications.

  • High performance: MongoDB's flexible data model and indexing capabilities allow for efficient querying and faster performance than traditional relational databases.

  • Easy to use: MongoDB has a simple and intuitive query language that makes it easy to retrieve data, and it has a large and active community that provides excellent documentation, support, and resources.

  • Open source: MongoDB is an open-source database management system, which means it is free to use and modify, and it provides access to the source code, enabling developers to customize it to their needs.

  • Cloud-ready: MongoDB has built-in support for cloud environments, making it easy to deploy and manage databases in cloud platforms like Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform (GCP).


Express.js: It is a minimal and flexible Node.js web application framework. Express helps us to do things such as URL routing and handling HTTP requests and responses.

Why use Express.js?

  • Improved productivity: Express.js provides robust features, such as middleware, routing, and templates, that simplify the development process and enhance productivity.

  • Customizability: Express.js is highly customizable, allowing developers to configure and structure their applications according to their needs and preferences.

  • Large community: Express.js is widely used and has a large community of developers, which means plenty of resources and libraries are available for solving everyday problems and extending its functionality.

  • HTTP handling: Express.js has excellent support for handling HTTP requests and responses, making it easy to create RESTful APIs and manage different data types.

  • Database integration: Express.js can integrate with various databases and ORMs, such as MongoDB, MySQL, and Sequelize, to provide data storage and retrieval capabilities.

  • Templating engines: Express.js supports multiple templating machines, such as Pug and EJS, which enable developers to generate dynamic HTML content and build user interfaces.

  • Simple API: Express.js has a simple and intuitive API, making it easy to learn and use, even for beginners.

Node.js: As an asynchronous, event-driven JavaScript runtime, Node.js is designed to build scalable network applications. It can handle many connections concurrently, and if there is no work to be done, Node.js will take a fairly low amount of resources to run. Take for example auto-scalable applications that increase their RAM and CPUs: they need more processing power to serve a higher load of requests and lower when the volume of requests decreases.

In a nutshell, we need Node.js in order to use Express.js, being the latter the technology we need to communicate back and forth with our front-end. By making HTTP requests from our front-end, we can connect to Express functions that will use MongoDB’s Node.js drivers to access data that we have in our MongoDB database.

Why use Node.js?

  • Scalability: Node.js is a lightweight and scalable runtime environment that allows developers to build fast, server-side applications using JavaScript.

  • Non-blocking I/O: Node.js has a non-blocking I/O model that enables developers to handle many concurrent connections without blocking the event loop and reducing the overall application performance.

  • Vast ecosystem: Node.js provides a vast ecosystem of modules, libraries, and frameworks that simplify the development process and help developers to achieve their goals faster.

  • Active community: Node.js has a vibrant and active community that constantly updates and improves the language and its tools, making it easier for developers to find solutions to their problems and stay updated with the latest trends.

  • Cross-platform: Node.js is cross-platform, which means that developers can build applications that run on various operating systems such as Windows, Mac, and Linux, reducing the development time and cost.

  • Versatility: Node.js can be used for various applications, including web servers, real-time applications, streaming applications, microservices, and more, making it a versatile tool for software development


React.js: It is an open-source, front-end JavaScript library for building user interfaces or UI components. By open-source, we mean that it is maintained by Facebook - now Meta - and a community of developers and companies. By using React, we can build our UI based on data from our back-end and render it as HTML.

Say you’re working for a cinema and have a database of when all the movies are going to be on, their time and date. You can create an information box that can take a movie title, movie time, and date, and you can make the front-end display the information box and feed in the data to populate it for any day of the week, any movie, any time.

Why use React.js?

  • Improved performance: React.js uses a virtual DOM to optimize performance, resulting in faster rendering of complex UI components and a smoother UX.

  • Component reusability: React.js provides a component-based architecture that promotes code reuse, making it easy to maintain consistency and scalability across different application parts.

  • Flexibility: React.js can be easily integrated with other libraries and frameworks, making it a flexible option for different project requirements and development environments.

  • Large community: React.js has a large and active community of developers, which provides extensive documentation, support, and resources for users worldwide.

  • Server-side rendering: React.js supports server-side rendering, which enhances SEO and improves page load times for users.

  • JSX syntax: React.js allows for using JSX, a syntax extension that enables developers to write HTML-like code within their JavaScript files, making it easier to read and write code.

  • Used by popular companies: React.js is used by many popular companies, such as Facebook, Instagram, and Airbnb, demonstrating its reliability and scalability for building large-scale web applications.


movies = [
     title: “Bambi”,
     time: 11.30,
     date: “04.03.2022”
     title: “Ghost”,
     time: 16.00,
     date: “04.03.2022”
     title: “Jaws”,
     time: 18.45,
     date: “04.03.2022”


Front-end result from the back-end code

Is MERN stack front-end or back-end?

Short answer: both. The MERN stack enables both the design, user experience (UX), and animation elements of the front-end, as well as the algorithmic and analytical part of the back-end.

This ends up being a benefit for companies as a single MERN stack developer is enough to get the job done, saving on recruitment costs.

Read also:

Is MERN stack in demand?

MERN stack is gaining popularity in recent years mostly because it uses the most in-demand technologies in the market. Also, there is no need to switch between the front-end and back-end environment, meaning that as a developer it’s enough to know JavaScript and JSON which will save you time, and allow you to complete a project quicker and much more efficiently. MERN stack is also more adaptable and easy to use in terms of code reusability or good performance.

4 things to remember when choosing a tech stack for your web development project

MEAN stack vs MERN stack

While both MEAN and MERN stack are open-source, JavaScript-based technologies, we can swap the client-side library on MERN and replace it with other front-end technologies, like the Angular framework - resulting in the MEAN stack, which now is a MongoDB, Express, Angular and Node stack.

Let’s compare the two to better understand their differences.


Since the MEAN stack makes use of Angular, the language used is TypeScript; on the other hand, MERN makes use of JavaScript or JSX.


Angular has been a very popular framework according to a 2021 survey by Stack Overflow, however, it must be noted that React is taking over and is at the top for most wanted framework, according to the same survey.


Angular is slightly better compared to React because Angular is a complete framework and React is just a JavaScript library. In order to make React more productive, you will have to make use of external third-party packages.

Upgrade path

Angular provides a CLI and a command-line interface known as the Angular CLI. This enables you to easily upgrade from one version to another. When it comes to React, it is much more difficult to upgrade because of the external third-party packages.

Note: For disruptive changes, CLI cannot be automatically upgraded; they usually provide examples and guidelines.

Learning curve

Both MERN stack and MEAN stack make use of MongoDB, Express.js, and Node.js, therefore the learning curve mainly depends on Angular and React. As already mentioned, React is purely based on JavaScript, making it much simpler to learn being suitable for beginners, and Angular has a more steep learning curve because you’re expected to learn an additional technology which is TypeScript, and is also more complex since it is a full web framework.

Data flow

Data binding is the mechanism that binds data sources from the provider and consumer together and synchronizes them. Using data binding, you will be able to manipulate elements present on the website using the browser.

While React only allows one-way data binding, Angular allows both one-way and two-way. One-way is a simple type of data binding where developers are allowed to manipulate the views through the models, which means that changes to the JavaScript code will be reflected in the corresponding HTML. On the other hand, two-way data binding allows your application to share the data in two directions - from the component to the template and vice versa. This makes sure that the models and views on your application are always synchronized.


As mentioned above, React makes use of third-party packages which allows you to select any package, however you will have to configure these packages which is an additional task. Angular, on the other side, is made up of components, thereby making it less flexible.


MEAN stack applications are much easier to test than MERN ones. This is because Angular applications can be tested using a single tool like Karma or Jasmin. On the contrary, to test MERN stack applications, you will have to use multiple testing tools; first, you will have to use Jest to test the JavaScript code and Enzyme for testing components, and so on.

Business benefits of MERN stack

Top brands and organizations are using MERN stack in their technologies like UberEats, Netflix, Facebook, Airbnb to name a few. These are some of the benefits they are getting a charge out of:

  • Seamless user experience
  • Accessible by Engineers
  • Community support
  • Less market hour for kickoff
  • Cost-effective
  • Time saving

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