WebSockets vs Rest API for real time data? Which to choose? | Software Interview Questions

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Choosing between WebSockets and REST API for real-time data depends on the specific requirements and constraints of your application. Here's a detailed comparison to help you decide which one is more suitable for your needs.

WebSockets

*WebSockets* is a protocol that provides full-duplex communication channels over a single, long-lived connection. It is designed for applications that require real-time, bidirectional communication.

*Key Characteristics:*

1. **Full-Duplex Communication**: Allows for simultaneous two-way communication between the client and server, making it ideal for real-time updates.
2. **Persistent Connection**: Once established, the connection remains open, allowing for continuous data exchange without the overhead of opening and closing connections.
3. **Low Latency**: Since the connection is persistent, data can be sent and received with minimal delay, which is critical for real-time applications.

*Use Cases:*

- **Chat Applications**: Real-time messaging where immediate communication is required.
- **Live Sports Updates**: Instant updates on scores, player statistics, and game events.
- **Financial Tick Data**: Real-time stock prices and market data.
- **Collaborative Editing**: Applications like Google Docs where multiple users need to see changes in real-time.

*Advantages:*

- **Real-Time Interaction**: Ideal for applications that require instant communication.
- **Reduced Latency**: Persistent connections reduce the time required to establish new connections.
- **Efficient Data Transfer**: Continuous connection allows for the efficient transfer of small messages without the overhead of HTTP headers.

*Disadvantages:*

- **Complexity**: Managing and maintaining WebSocket connections can be more complex compared to stateless HTTP connections.
- **Scalability**: Requires careful consideration for scaling, as each client maintains an open connection to the server.
- **Resource Intensive**: Long-lived connections can consume more server resources compared to stateless HTTP requests.

REST API

*REST (Representational State Transfer) API* is an architectural style that uses standard HTTP methods (GET, POST, PUT, DELETE) for communication. It is stateless, meaning each request from the client to the server must contain all the information needed to understand and process the request.

*Key Characteristics:*

1. **Stateless**: Each request is independent and contains all the information needed for the server to fulfill it.
2. **Scalability**: Statelessness makes it easier to scale horizontally by adding more servers.
3. **Cacheable**: Responses can be cached to improve performance.

*Use Cases:*

- **CRUD Operations**: Typical Create, Read, Update, and Delete operations on resources.
- **Service Integration**: Communication between microservices or third-party APIs.
- **Periodic Updates**: Applications that can tolerate some delay, like social media feeds or news updates.

*Advantages:*

- **Simplicity**: Easier to implement and use, especially for standard CRUD operations.
- **Scalability**: Statelessness simplifies horizontal scaling.
- **Interoperability**: Uses standard HTTP methods, making it widely compatible and easy to integrate with various clients and services.

*Disadvantages:*

- **Latency**: Each request/response cycle introduces latency, making it less suitable for real-time applications.
- **Overhead**: Each HTTP request includes headers, which can add unnecessary overhead for small, frequent updates.
- **Polling**: For real-time data, clients may need to poll the server frequently, which can be inefficient and lead to higher latency.

When to Choose WebSockets

- **Real-Time Communication**: When you need low-latency, bidirectional communication.
- **Interactive Applications**: Chat apps, online gaming, live updates (sports, financial data), collaborative tools.
- **Continuous Data Streams**: Applications that require a steady stream of data from the server to the client.

When to Choose REST API

- **Stateless Interactions**: When each request is independent, and you don’t need persistent connections.
- **Resource Management**: Standard CRUD operations on resources.
- **Service Integration**: When integrating with other services or APIs that follow REST principles.