REST, or REpresentational State Transfer, is an architectural style for providing standards between computer systems on the web, making it easier for systems to communicate with each other. Roy Fielding first presented it in 2000 in his famous dissertation. Since then it has become one of the most widely used approaches for building web-based APIs (Application Programming Interfaces).

Types of API design patterns

APIs are contracts that define how applications, services, and components communicate.API design patterns provide a shared set of best practices, specifications, and standards that ensure APIs are reliable and simple for other developers to use.

API Design Patterns reveal best practices for building stable, user-friendly APIs. These design patterns can be applied to solve common API problems and flexibly altered to fit your specific needs. Hands-on examples and relevant use cases illustrate patterns for API fundamentals, advanced functionalities, and even uncommon scenarios.

Following are some of the commonly used API design patterns:

RESTful API

• Uses HTTP methods to interact with resources
• Supports caching and scalability
• Works well for CRUD (Create, Read, Update, Delete) operations
• Allows for stateless communication between client and server
• Can be used with a variety of programming languages and frameworks

GraphQL API

• Allows clients to request exactly the data they need
• Provides a single endpoint for clients to make requests
• Can reduce the number of requests needed to get all required data
• Can be more complex to implement than RESTful API
• May require additional tooling and libraries

RPC API

• Uses Remote Procedure Calls to interact with a remote server
• Typically requires a protocol or API definition, such as Protobuf or gRPC
• Can be more efficient than RESTful API in terms of network usage
• Can be more difficult to implement and maintain

Event-driven API

• Sends notifications to clients when certain events occur
• Can reduce the need for clients to repeatedly poll for updates
• Can be useful for real-time applications
• Can be more difficult to implement and maintain

Message Queue API

• Allows applications to send and receive messages asynchronously
• Can provide a reliable and scalable way to process messages
• Can be useful for distributed systems
• May require additional infrastructure and tooling

SOAP API

• Uses a messaging protocol to exchange structured information
• Can be used with a variety of programming languages and frameworks
• Can support more complex operations than RESTful API
• Can be more difficult to implement and maintain

Hypermedia API

• Includes links between resources, allowing for dynamic discovery and navigation
• Can improve the flexibility and adaptability of an API
• May require additional tooling and libraries
• Can be more difficult to implement and maintain

Decision of API design pattern will depend on the specific needs of the project and the system architecture. RESTful API is often a good choice for simple CRUD operations, while GraphQL may be a better choice for complex queries. RPC API and SOAP API can be more efficient for certain types of operations but can be more complex to implement and maintain. Hypermedia API, event-driven API, and message queue API can be useful for certain types of systems and applications but may require additional tooling and infrastructure.

REST API Design Patterns

When creating API projects, companies like to use the best practices and guidelines for web services based on REST.

REST (Representational State Transfer) API (Application Programming Interface) design patterns are a set of best practices and conventions for designing web services. They follow the principles of the REST architectural style. These patterns help organize the endpoints, resources, and data models of RESTful APIs to make them simple, scalable, and easy to use. Some common patterns in REST API design include:

Resource-Based

This pattern organizes API endpoints around the different parts of the system that the API reveals or shares, called resources.

CRUD (Create, Read, Update, Delete)

This pattern is a common way of describing the four main operations (create, read, update, delete) that can be done on a resource.

HATEOAS (Hypermedia as the Engine of Application State)

This pattern includes hyperlinks in API responses that let clients discover and navigate the API resources.

Filter and Pagination

This pattern adds filtering and pagination features to help clients efficiently get specific parts of data from a resource.

Versioning

This pattern provides various versions of an API to accommodate changes in the API without disrupting existing clients.

I will recommend to watch this video for getting a really fresh and clear perspective for REST

REST 6 design principles

CLIENT SERVER ARCHITECTURE

The client-server design pattern ensures that the client and server components can develop independently. This is done by separating the responsibilities of the user interface (client) and data storage (server).

When we separate the user interface from data storage, it becomes easier to use the user interface on different platforms. Additionally, simplifying the server components improves scalability.

However, it’s crucial to ensure that the communication interface or contract between the client and server remains stable as both components evolve over time. This prevents any disruptions in their interaction.

STATELESSNESS

Statelessness This rule requires that every request from the client to the server includes all the information needed to understand and fulfill the request. The server can’t rely on any context information stored on its side. Therefore, the client application is responsible for maintaining the entire session state.

CACHEABILITY

The cacheable constraint means that a response must clearly indicate whether it can be cached or not.

If the response is marked as cacheable, the client application is allowed to reuse the response data for similar requests within a specified period.

LAYERED SYSTEM

The layered system style enables building an architecture with hierarchical layers by restricting how components behave. In this setup, each component is limited to interacting only with the layer immediately above or below it.

A simple example of a layered system is the MVC (Model-View-Controller) pattern. It separates concerns, making it easier to develop, maintain, and scale an application.

CODE ON DEMAND

REST also permits the expansion of client functionality by downloading and running code, such as applets or scripts.This downloaded code helps simplify clients because it reduces the need for pre-implemented features. Servers can deliver a portion of the required features to the client in the form of code, and the client only has to execute that code.

UNIFORM INTERFACE

Applying the principle of generality to the components’ interface simplifies the overall system architecture and makes interactions more visible. Various constraints contribute to achieving a consistent REST interface:

1. Identification of resources – Each resource in the interaction between the client and the server must have a unique identifier in the interface.

2. Manipulation of resources through representations – Resources should have consistent representations in server responses, and API consumers should use these representations to modify the resource state on the server.

3. Self-descriptive messages – Resource representations should contain enough information to describe how to process the message and provide details on additional actions that the client can perform on the resource.

4. Hypermedia as the engine of application state – The client should only have the initial URI of the application, and it should dynamically navigate other resources and interactions using hyperlinks.

In simpler terms, REST establishes a consistent and uniform interface for interactions between clients and servers. For instance, HTTP-based REST APIs use standard HTTP methods (GET, POST, PUT, DELETE, etc.) and URIs (Uniform Resource Identifiers) to identify resources.