API and API Design: What are Real-time APIs?

In partnership with

Hello “👋

Welcome to another week, another opportunity to become a Great Backend Engineer.

Today’s issue is brought to you by Masteringbackend → A great resource for backend engineers. We offer next-level backend engineering training and exclusive resources.

Before we get started, I have a few announcements:

I have a special gift for you: You will love this one.

As developers, we are great at building products but selling them becomes a problem because “We hate marketing”?

For me:

I have been able to crack some of my marketing troubles, especially in the aspect of Copywriting following a book published by the founder of Vec Studio.

If you will someday or now enter into the world of CodePrenuers then this book is for you.

It’s 100% free

Click here to download the book

Drowning In Support Tickets? Maven AGI is here to help.

Maven AGI platform simplifies customer service by unifying systems, improving with every interaction, and automating up to 93% of responses. Seamlessly integrated with 50+ tools like Salesforce, Freshdesk, and Zendesk, Maven can deploy AI agents across multiple channels—text, email, web, voice, and apps—within days. Companies like Tripadvisor, ClickUp, and Rho slash response times by 60%, ensuring quicker support and exceptional customer satisfaction. Don’t let support tickets slow you down

Request a free personalized demo today.

Modern applications increasingly demand live updates and instantaneous communication. Whether it’s receiving stock market price changes or chatting with friends in a messaging app, Real-time APIs have become a critical part of delivering up-to-the-second information.

Imagine seeing a live match and there was a goal where Messi scored and your SportyBet app hasn’t updated it with your bet in it.

How will you feel?

Now that’s the importance of Real-time APIs and why you need to understand how it works and how to build one yourself as a backend engineer.

In this article, we’ll explore how Real-time APIs work, common use cases, architectural considerations, and some best practices for effective design.

What Are Real-time APIs?

At a high level, Real-time APIs are interfaces that push data to clients as soon as new information is available. Instead of sending a request and waiting for a response (as is typical in REST-based interactions), Real-time APIs keep the connection open, allowing the server to publish updates instantly.

There are key characteristics of Real-time APIs and these characteristics give birth to the different types of real-time APIs we will discuss later.

• Persistent Connections: The client and server maintain a long-lived connection, often through WebSockets, Server-Sent Events (SSE), or other protocols that enable continuous communication.

• Bi-directional or Uni-directional Flows: In some cases (e.g., WebSockets), both client and server can send messages at any time. In others (e.g., SSE), data flows primarily from the server to the client.

• Event-driven Updates: The server broadcasts changes—such as a new chat message or a price update—as events that subscribed clients can act upon immediately.

Common Use Cases

I have already mentioned a few use cases. However, if your project falls under any of the categories listed below. Then you should consider using real-time APIs to build them.

• Live Chat and Messaging Apps
  Platforms like WhatsApp, Slack, or Microsoft Teams use Real-time APIs to deliver messages instantly to participants. As soon as a user sends a message, the server propagates it to all connected clients in real-time.

• Financial Trading Platforms
  Stock trading and cryptocurrency exchanges rely on real-time updates to track price fluctuations or order book changes. The difference of a few milliseconds can be crucial in high-frequency trading environments.

• Online Multiplayer Games
  Multiplayer games demand constant state synchronization among players. Real-time APIs handle position updates, score changes, and other game-state events to ensure a smooth experience.

• Collaborative Tools
  Document editing apps (like Google Docs) allow multiple users to edit the same file simultaneously. Real-time APIs power live updates, highlighting where others are editing and showing changes as they happen.

How Real-time APIs Work

Establishing a Persistent Connection

• WebSockets: A full-duplex protocol allowing both the client and server to send data at any time. WebSockets begin as an HTTP handshake, then upgrade to a more efficient TCP-based protocol.

• Server-Sent Events (SSE): A one-way channel from server to client. The client subscribes to a stream of events, and the server continuously sends updates as text-based messages.

• Long Polling: Not truly a persistent connection, but an emulation of real-time behavior where the client sends a request that the server holds open until data is available.

We will discuss these types of real-time APIs in complete detail in the upcoming newsletters.

2. Data Transfer in Real Time

Once the connection is established, the server sends updates to the client whenever new data is available. If using a full-duplex protocol (e.g., WebSockets), the client can also send data to the server without initiating a new request each time.

3. Maintaining Connection State

Real-time APIs need to manage connections, handling scenarios such as:

• Connection Loss: Detecting disconnections and re-establishing when the client comes back online.

• Scaling: Balancing load across multiple servers while keeping messages consistent and ordered.

Example of Real-time Chat with WebSockets

Below is a simplified Node.js/Express server illustrating how a chat application might handle real-time communication using WebSockets:

const express = require('express');
const http = require('http');
const WebSocket = require('ws');

const app = express();
const server = http.createServer(app);
const wss = new WebSocket.Server({ server });

wss.on('connection', (ws) => {
  console.log('New client connected');

  ws.on('message', (message) => {
    console.log(`Received: ${message}`);
    // Broadcast to all clients
    wss.clients.forEach((client) => {
      if (client.readyState === WebSocket.OPEN) {
        client.send(message);
      }
    });
  });

  ws.on('close', () => {
    console.log('Client disconnected');
  });
});

server.listen(3000, () => {
  console.log('Server is listening on port 3000');
});

The code above uses the WebSocket server to create a connection and await the client’s messages after connection.

Real-time APIs are vital in scenarios where milliseconds matter—chat apps, financial dashboards, gaming, and collaborative platforms. By maintaining open connections and allowing continuous data exchange, they deliver a seamless, interactive user experience. However, designing such APIs requires careful attention to scalability, security, and connection management.

Did you learn any new things from this newsletter this week? Please reply to this email and let me know. Feedback like this encourages me to keep going.

See you on Next Week.

Remember to start learning backend engineering from our courses:

Get a 50% discount on any of these courses. Reach out to me (Reply to this mail)

1. Become a Node.js Backend Engineer is Live

2. Become a Rust Backend Engineer is Live

3. Become a Python Backend Engineer is Live

4. Become a Java + Spring Backend Engineer is Live

Top 5 Remote Backend Jobs this week

Here are the top 5 Backend Jobs you can apply to now.

👨‍💻 BlueCat
✍️ Backend Engineer
📍Remote, Serbia
💰 Click on Apply for salary details
Click here to Apply for this role.

👨‍💻 Constructor
✍️ Backend Engineer: Experiments Team (Remote)
📍Remote, Worldwide
💰 Click on Apply for salary details
Click here to Apply for this role.

👨‍💻 Homepage
✍️ Backend Developer PHP
📍Remote, Worldwide
💰 Click on Apply for salary details
Click here to Apply for this role.

👨‍💻 Monzo
✍️ Backend Engineer
📍Remote
💰 Click on Apply for salary details
Click here to Apply for this role.

Want more Remote Backend Jobs? Visit GetBackendJobs.com

Backend Engineering Resources

1. Backend Engineering Hub

2. All Backend Books

3. Visit our Backend Store

4. Join our Community

5. Backend Engineering Courses

LAST WORD 👋 

How am I doing?

I love hearing from readers, and I'm always looking for feedback. How am I doing with The Backend Weekly? Is there anything you'd like to see more or less of? Which aspects of the newsletter do you enjoy the most?

Hit reply and say hello - I'd love to hear from you!

Stay awesome,
Solomon

I moved my newsletter from Substack to Beehiiv, and it's been an amazing journey. Start yours here.