RESTful Principles in the Age of Microservices

Back in 2017, I was on stage at the code.talks conference in Hamburg and shared my experiences of implementing microservices with Nodejs in real-world customer projects. The interest in this topic and the many questions at the end of the session were overwhelming.

Today, the landscape has evolved significantly. Microservices are not a one-size-fits-all solution, but their impact is undeniable. They have introduced monitoring tools and patterns for debugging in a distributed environment, improved our knowledge of APIs, and paved the way for the rise of containers and serverless computing.

Gone are the days when a tiny code change could jeopardize the entire application. Remember the lengthy and tedious deployments of even the smallest changes? Such challenges have driven our pursuit of excellence. Throughout my time in software development, topics like automation in deployment, readable and maintainable code, but also reduction of complexity were my main topics that drove me to constant development and improvement.

Today, I’ll take an in-depth look at microservices and RESTful APIs. These vanguards of modern development promise scalability, agility, and faster deployments. Let’s go!

What are Microservices?

Saying it simple, microservices are about decomposing applications into small services that run independently. But what exactly does it mean? Sam Newman, a leading voice in this space, beautifully summarizes it as:

Small autonomous services that work together, modeled around a business domain.

Breaking this down:

• Small & Autonomous: Microservices are designed to be concise. Each service does one thing and does it well. Being autonomous means they operate independently, reducing dependencies and ensuring that a hiccup in one service doesn’t bring the whole system down.
• Work Together: While each service stands alone, they aren’t isolated. They collaboratively achieve larger goals by communicating with each other. Think of them as players in an orchestra, each playing their part, but collectively creating a symphony.
• Modeled Around a Business Domain: This is the essence of microservices. Instead of structuring around technical capabilities (like databases or frontend), they’re structured around business functionality — like billing, user management, or inventory. This makes them aligned closely with business needs, ensuring that changes in business strategy can be quickly reflected in the software.

In a nutshell, microservices take the complexities of modern software requirements and break them into manageable, independent units that collaboratively deliver value.

What are RESTful APIs?

If you've ventured into web development, you've likely encountered RESTful APIs. But what exactly are they?

REST stands for Representational State Transfer, while API means Application Programming Interface.

In essence, a RESTful API is a method for software systems to communicate using REST principles. Developed by Roy Fielding, this concept has become a popular approach for designing web interactions. RESTful APIs act as interpreters, enabling various technological components to understand each other, thus enhancing our online experiences.

Let's delve into the guiding principles of RESTful Web Services' architectural style.

Read also What is an API?

Architectural Constraints of RESTful API

When we talk about RESTful APIs, it’s essential to recognize the foundation upon which they’re built: the five architectural constraints. These aren’t just arbitrary rules; they’re pivotal guidelines that make a web service “RESTful.” Let’s break each one down:

Uniform Interface

Having a consistent interface is like having a universal remote for all your devices. It simplifies interactions for both the client and server, ensuring that no matter which resource is being accessed, the method of interaction remains the same. This predictability fosters stability and streamlines the integration of different services.

Stateless

In RESTful services, each request from a client contains all the information the server needs to understand and process that request. Think of it as sending a letter with all details every time, rather than assuming the recipient remembers past letters. This approach ensures that no client information is stored between requests, making interactions independent and straightforward.

Cacheable

Speed and efficiency are crucial in the digital world. When data is labeled as “cacheable,” it means the client can store that response for a set period. By doing this, not every request needs to go all the way to the server. Some can be handled locally from the cache, speeding up response times and reducing server load.

Client-Server

The essence of this constraint is the separation of concerns. The client handles the user interface and user experience, while the server manages the data. This separation allows both the client and server to develop and scale independently. It’s like having a cook specialized in preparing food and a waiter specialized in serving it, each honing their particular skill.

Layered System

Imagine a multi-layered cake. You see the top layer, but beneath are multiple layers, each with its role. In REST, a client doesn’t need to know about the intricate layers of an API — it interacts with the top layer. This abstraction promotes security, as internal layers remain hidden, and also facilitates modularity and scalability.

In essence, these five constraints aren’t just checkboxes for an API to be deemed “RESTful.” They’re vital principles shaping the efficiency, scalability, and flexibility of RESTful services, ensuring they’re robust and future-ready.

Microservices in the Context of RESTful APIs

Microservices, by nature, align seamlessly with RESTful APIs. Both emphasize decoupled, scalable, and flexible systems. But when combined, they create a formidable partnership, addressing challenges in modern software development. Let’s discuss how microservices derive value when integrated with RESTful principles.

Decoupled Design

Microservices’ core principle is creating small, autonomous services that center around specific business functionalities. RESTful APIs promote a similar mindset with its client-server constraint: the client focuses on the user interface, and the server deals with data processing. When we combine these approaches, we get systems where changes in one service (or its interface) don’t ripple and cause disruptions across the board. The result? A more agile and resilient application.

Scalability

Both RESTful APIs and microservices address scalability but from slightly different angles. While microservices can be independently scaled based on their specific loads, RESTful principles like statelessness ensure that every request is treated as a new one, without relying on stored sessions. This makes scaling out more manageable, as incoming requests can be directed to any available instance of a service.

Easier Troubleshooting

RESTful APIs emphasize a consistent and uniform interface. When paired with microservices, this means each service offers a predictable interaction model. When issues arise, developers don’t have to grapple with disparate communication styles across services. They know what to expect, simplifying debugging and issue resolution.

Improved User Experience

Combining the modular nature of microservices with the caching constraint of RESTful APIs can significantly improve the user experience. Data that is accessed frequently can be cached on the client side, making applications faster and more responsive. At the same time, the modular architecture ensures that only the needed services are invoked, conserving resources.

Flexibility in Development

RESTful principles aren't tied to specific technologies. When combined with microservices, you have a system where each service can be written in the language best suited for its functionality. Need a service for heavy data processing? C#, Spring Boot, or Rust might be the right choice. Is another service more CRUD-oriented? Python or Node.js could be better suited. This combination encourages using the right tool for the job.

Conclusion

Microservices and RESTful APIs aren't just buzzwords—they complement each other perfectly. Together, they create a system that's scalable, maintainable, and efficient. For developers and enterprises aiming to stay agile and responsive in a dynamic technology landscape, this partnership adds significant value.

Cheers!