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The Complete Guide on MERN Stack

The Complete Guide on MERN Stack

Over time, some development stacks have become go-to choices for devs and teams. And one of these high-ranked options is no other than the combination of MongoDB, Express.js, React, and Node. But what is the MERN Stack? How does each of its techs work to create complete products? We'll delve into this great stack so you can see it for yourself! 

What is the MERN Stack?

MERN Stack is a combination of four technologies: MongoDB, Express, React, and Node. Each represents different application layers, and by working together, these techs can create a full-stack JavaScript development environment and end-to-end JavaScript applications. This advantage narrows down the complexity of big-sized products despise project requirements.

Often, the MERN stack receives praise for its simplicity, as it allows developers to use a single programming language throughout the entire application stack. It has gained popularity for building modern, real-time web applications. Since it leads to faster application development, it's broadly used in the software development industry.

MERN Stack Elements

MongoDB on MERN

MongoDB is a popular open-source, document-oriented NoSQL (non-relational) Database Management System. Within the MERN Stack, Mongo is essential to store data, such as content, user profiles, or uploads. It stores data in flexible documents depending on the project requirements, allowing for dynamic schemas and easy application integration.

This document database has wide uses in several applications, such as Content Management Systems, real-time analytics, eCommerce platforms, and mobile applications. It's also helpful in Progressive-Web and Single-Page Applications. In short, it's an amazing tool for any project that needs flexible and scalable data storage! Further, it works great with the other techs in this stack! Mongo supports scalability and agility and has speedy query language performance.

MongoDB Features

Document-Oriented. MongoDB stores data in flexible documents, similar to JSON objects. Each document can have its structure, and fields can vary between documents. Likewise, MongoDB can scale horizontally across multiple servers, allowing for increased performance as data grows. It uses a sharding mechanism to distribute data across different machines.

Performance and Availability. MongoDB is optimized for performance and can handle a high volume of read and write operations. It supports various indexing options to improve query performance. Further, MongoDB supports replica sets, groups of database nodes that maintain identical copies of data, ensuring high availability in case of node failures.

Programming Languages. MongoDB provides official drivers for various programming languages, making interacting with the database from different application environments easy. The official drivers' list goes from application frameworks to query languages!

Express.js on MERN

Express.js is a popular server-side web application framework for Node.js. The minimalistic and unopinionated framework provides flexible features for building web applications and APIs. Further, it's asynchronous, single-threaded, efficient, fast, and scalable. ExpressJS provides server-side logic for apps, applying to single-page, multipage, and hybrid web apps.

The framework gest used widely in the Node.js community for developing web applications, RESTful APIs, and single-page applications. Its simplicity, flexibility, and extensive ecosystem make it popular for building server-side applications with Node.js. 

Express.js Features

Routing. Express.js allows you to define routes to handle different HTTP methods (such as GET, POST, PUT, and DELETE) and URLs. It provides a simple and intuitive way to map URLs to specific functions or handlers processing requests.

Middleware. Middleware functions in Express.js can be executed sequentially in the request-response cycle. These can perform various tasks like parsing request bodies, handling authentication, logging, and error handling. Middleware functions can access the request and response objects and modify them or pass control in the chain. Further, Express.js has a rich ecosystem of middleware libraries that can be easily integrated into your application, providing additional functionality. This feature is handy for authentication, session management, and input validation.

Template Engines. Express.js supports template engines like EJS, Handlebars, and Pug (formerly Jade). These template engines allow dynamically generating HTML pages by embedding data within templates. Moreover, Express simplifies serving static assets to clients directly from a directory, such as images, CSS stylesheets, and JavaScript files.

React on MERN

Although many think of React js as a framework, it's a front-end JavaScript library. Most known as React, this open-source library focuses on building interactive User Interfaces (UIs). React follows a component-based approach, allowing developers to create reusable UI components that efficiently update and render when data changes. Its main features include being declarative, simple, server-side supporting, and component-based. 

Since its launch, it's been a top-rated tool for development companies of all sizes. React is often used with other frameworks or libraries like Redux to build feature-rich and scalable web applications. It has gained great popularity in the web development community due to its efficient rendering, components reusability, and large supporting ecosystem.

React Features

Component-Based Architecture. React breaks the UI into reusable components. Each component compresses its logic and state to build and maintain complex interfaces easier. Also, components can be nested within each other, forming a hierarchical structure. Another interesting fact is that React components have states to represent their data states. When the state changes, React's state management automatically re-renders the component and updates the UI accordingly.

Virtual DOM. React utilizes a virtual representation of the Document Object Model (DOM). This lightweight copy of the actual DOM, maintained by React, allows for efficient updates and component rendering. React compares the virtual DOM with the real DOM and only updates the necessary parts when changes occur, resulting in improved performance.

Data Flows. React follows a unidirectional data flow pattern, also known as one-way binding. Data flows from parent to child components through props (properties), ensuring predictable and easy-to-understand data flow within the application.

Node.js on MERN

Node—or Node.js—is an open-source JavaScript runtime environment for scalable network apps. Built on the Chrome V8 JavaScript engine, Node is asynchronous and event-driven. Also, it's cross-platform, single-threaded, fast, and scalable. Node’s benefits include improved stack developer productivity and satisfaction while cutting development costs.

The Node.js environment allows developers to run JavaScript code outside the browser and on the server. Moreover, it has an easy learning curve and a large community. If you want to see an example of Node in action, you can look at our work with Marathon Kids!

Node.js Features

Asynchronous and Event-Driven. Node.js follows a non-blocking, asynchronous programming model. It uses an event-driven architecture, allowing multiple I/O operations to be processed concurrently without blocking the execution of other tasks. This feature makes it well-suited for handling a wide range of concurrent connections for highly scalable applications. Its event-driven architecture provides excellent scalability and performance. 

Node Package Manager. Node's npm comes bundled with Node.js and provides access to a vast ecosystem of reusable open-source libraries and modules. As a result, it allows developers to integrate third-party code into their applications easily.

Cross-Platform. Node.js is cross-platform, supporting Windows, macOS, and various Linux distributions. This highlight lets developers write code once and run it on different operating systems without requiring significant modifications. The benefits of this feature apply to web servers, APIs, real-time applications, and more.

How does the MERN Stack work?

The MERN Stack uses a 3-tier architecture comprising Front-End, Back-End, and database. The Front-End display tier of the application uses React. As mentioned, React's dynamic client-side application components are responsible for rendering the User Interface and handling user interactions. Contrariwise, Express works as the backend server, handling incoming requests and performing server-side logic, including all the project files and documentation.

With both ends covered, Express communicates with the database to store and retrieve data. In this stack, MongoDB works as the Database tier, providing a flexible schema and allowing easy integration with the other components. Lastly, while all this happens, Node acts as the runtime environment for the server-side code, allowing the server-side execution of JavaScript. Let's divide this process into steps to get an easier view of how the MERN Stack techs interact with one another! Typically, the MERN Stack application tier's flow goes as follows:

1. The client (React) sends a request
2. The server (Express) routes and processes the request
3. Express notifies MongoDB (the warehouse) to fetch or update data
4. The server responds to the client with the requested data or operations
5. React receives the data and updates the UI for a seamless User Experience!

At all stages, Node acts as an intermediary between the client and server. It ensures the smooth execution of server-side code, allowing request processing, response generation, and seamless integration. With Node.js, devs can leverage JS power throughout the process, leading to full-stack technology projects without switching languages.

MERN Stack with React Native

Are you wondering if you can create mobile apps with the MERN Stack? The answer is yes! Yet, you must add React Native. To give you a bit of context, React Native is an open-source framework built over React, specializing in mobile application development. Like its parent library, it focuses on code reusability by having functional components. Likewise, it's great as a client-side JavaScript framework! Both these features lead to a remarkable ability to build. Moreover, it's cross-platform, meaning you can use it for iOS and Android! With this React application, you can lean on faster development of smaller applications, which includes native interface creation and easy testing.

​Why use the MERN Stack?

What makes the MERN Stack so great? We’ll cover the pros of combining these four techs.

Full JavaScript Stack. The MERN stack allows teams to use a single programming language, JavaScript, for both the front and the back end. This advantage simplifies development processes and reduces the learning curve. By using the MERN stack, developers can leverage the power of JavaScript throughout the entire application stack, from the front end to the database, allowing for efficient development and code reuse.

Rich Ecosystem. React and Node have large and active communities, meaning numerous libraries, frameworks, and tools are available to enhance stack developer productivity. For example, the npm package manager provides access to a vast repository of open-source packages that easily integrates into MERN stack applications. Further, the MERN Stack itself has an extensive community. Its extensive documentation, tutorials, and resources make it easier for full-stack developers to find solutions, troubleshoot, and stay updated.

Scalability and Performance. Node.js' non-blocking, event-driven architecture allows managing many connections with low memory overhead. As a result, its products are highly scalable and well-suited for building high-performance applications. Also, it enables handling heavy loads and real-time interactions. Following this path, MongoDB offers data modeling and schema design flexibility. It easily takes unstructured or rapidly evolving data and enables fast prototyping and iterative development. Likewise, React's component reusability ensures that specific server-side changes don't affect the building user interface process.

Overall, the MERN stack offers a streamlined, faster development process, efficient UI rendering, scalability, and a large ecosystem of tools and libraries. It's a robust choice for building modern, real-time, data-driven, and JavaScript-based web applications. Its broad list of advantages also makes it an ally for Agile Development and its different methodologies! 


The MERN Stack is a powerful technology with many advantages for development and business. Also, given that all four tools work with JavaScript, the learning process is more accessible while offering a full-stack solution. As a result, devs, teams, and companies can leverage the power of one of the most well-known programming languages to create top-notch, disruptive products. We hope this article has given you a clear overview of the MERN Stack for your next full-stack development project!