How To Build Scalable Real-Time Applications With JavaScript
Real-time apps provide real-time reporting and analytics to help businesses make faster and more informed decisions, while also offering a better user experience and enhanced security.
This article will consider the challenges and solutions of building scalable real-time applications with JavaScript in 2024, focusing on WebSocket implementation, server-sent events (SSE), and libraries like Socket.IO to manage real-time communication effectively. Likewise, we will also consider the best practices for handling data synchronization, ensuring low latency, and maintaining scalability as user demand grows.
The Need for Real-Time Applications
An increasing number of industries are becoming reliant on real-time applications (RTAs), as companies strive for higher speeds in terms of communication and decision-making. From a consumer perspective, RTAs provide a better user experience (UX), enabling organizations to issue faster responses to queries and assess live data to improve operational performance and efficiency.
However, building real-time applications does come with challenges, especially when it comes to handling latency and performance. Users expect a response within less than 4 seconds and have an extremely low tolerance for any latency. To avoid these issues, many developers turn to JavaScript to deliver high-performance, low-latency RTAs.
Real-Time Applications: Key Challenges
As real-time applications are expected to deliver an experience that provides practically instantaneous responses, any issues regarding performance and latency need to be completely ironed out before deployment. Below are several challenges that could impair the performance and usability of RTAs and how they can be overcome.
- Latency, the delay before data transfer begins, is often caused by network congestion, slow server processing times, or misconfigured data transmission protocols. To mitigate this, a developer needs to remove all barriers that may slow the transfer of data between the user’s device and the application server.
- Synchronization issues can arise when multiple users attempt to perform an action at the same time — for example, during an online multiplayer game. This requires developers to ensure that any in-app interactions are sequenced correctly and accurately across all connected devices.
- Scalability can be a challenge when the user base of an RTA grows. It can impact a JavaScript developer when the app’s database fails to handle larger volumes of data and user requests. This could be a result of poor resource utilization, with some app components experiencing a higher workload than others.
- Security and scalability often go hand-in-hand in real-time applications. Therefore, as an RTA’s user base increases, so does its attack surface. To combat this, developers need to increase monitoring and observability, secure APIs, and implement robust cloud security practices to ensure that as an application scales, data and services remain secure against potential threats.
Building Scalable Real-Time Applications With JavaScript in 2024
Node.js is often the preferred runtime environment for JavaScript developers, as it is open source and backed by impressive community support. Even global giants such as Uber are developing their apps with the help of Node.js, favored for its single-threaded processing capabilities to effectively handle over 2 million remote procedure calls (RPCs) per second.
Of course, most RTAs will never reach such a scale; but regardless, any application needs to be built with future expansion in mind. In this section, we will discuss the innovative solutions that developers need to know before developing a scalable real-time application with JavaScript.
Creating Real-Time Apps With WebSocket
When you choose to build your RTA in a runtime environment such as Node.js or use a framework such as Next.js, it is recommended to implement WebSocket. WebSocket is a communication protocol that enables full-duplex communication channels over a single TCP connection. In contrast to HTTP, WebSocket is bi-directional, allowing both the client and server to initiate data transfers — allowing for real-time interaction. Likewise, the protocol is well-known for its:
- Low Latency: Data can be transferred instantly to create an enhanced user experience.
Efficient Performance: WebSocket does not establish a new connection for each interaction, further reducing delays within real-time applications. - Bi-Directional: Both the client and server can send data simultaneously without needing to wait for a request.
Although the performance benefits of WebSocket are numerous, the protocol is not without vulnerabilities in terms of security. This is why developers must always adhere to security best practices when developing RTAs in JavaScript, implementing measures such as data validation, input sanitization, access control, and authentication.
By establishing a robust security strategy, common threats such as cross-site scripting (XSS) attacks, cross-site request forgery (CSRF) attacks, and session hijacking can be prevented.
WebSocket is a powerful solution for developing real-time, interactive, dynamic, and collaborative RTAs, making it easy to issue live updates and facilitate instantaneous interactions. This level of performance ensures applications built in WebSocket can be easily scaled with no impact on data transfer speeds and the user experience.
Using Server-Sent Events (SSE) for Real-Time Updates
Server-sent events (SSE) is an HTTP-based technology that provides developers with an API called EventSource, allowing applications to easily connect to the server and provide updates from it. This is an advanced solution if a real-time application requires more complex updates, as opposed to simple text alerts or new price updates. For standard updates, WebSocket is more than sufficient.
SSE is also uni-directional, unlike WebSocket, and events are not available in binary — only UTF-8. However, two key advantages SSE has over WebSocket are built-in support for automatic reconnection and event ID tracking. This means that if there is a disconnection, an attempt to reconnect will be made automatically, while event ID tracking ensures no messages are lost during the disconnection.
SSE is less flexible than WebSocket, but could be a preferable solution when building real-time applications that have a simple use case that predominantly focuses on sending live updates and does not require frequent client-to-server requests.
Socket.io (Event-Driven Libraries)
Socket.io is an event-driven library that facilitates real-time, bi-directional communication between a client and the server. In addition to being a library, Socket.io is also a protocol that can be implemented with Node.js, using WebSocket to provide its core functionality.
However, Socket.io improves on the standard WebSocket offering with additional features such as heartbeat and timeouts. Heartbeat is a mechanism that continuously checks that there is an established connection between client and server. Meanwhile, timeouts — similar to the Node.js EventEmitter — set a timeout on the connection to the server to avoid an indefinite wait period, which can impair the user experience.
In most cases, Socket.io improves on WebSocket by providing additional functionality such as automatic reconnections and the ability to broadcast an event (such as an alert) to all connected users simultaneously. This makes Socket.io a popular choice for live chat and instant messaging applications, although the library has a wide range of use cases.
Conclusion
The versatility of JavaScript makes it a popular choice for developers when building scalable real-time applications, supported by communication protocols such as WebSocket, which can be made even more powerful with an event-driven library like Socket.io.
These solutions ensure RTAs have low latency and high performance, while facilitating bi-directional communication to avoid challenges such as synchronization issues.
When building scalable RTAs, security must also be a key consideration, following best practices to ensure that each data transfer is validated and encoded, and all users are authenticated.
