How to Write Scalable Backend Applications

So, you’ve built a website, you have a lot of visitors, and a high conversion rate from visitors to customers. But over time, your server stops handling the load, adding new features gradually becomes more difficult, and refactoring is not a viable option. Why does this happen? And how do you write backend applications that can be easily scaled?

Building a server is somewhat similar to building houses.

Without a solid foundation, a structural frame with load-bearing walls, and well-planned room layout, the house won’t withstand bad weather. Backend applications are built on a foundational HTTP server, with routers and controllers serving as the structural components, and services representing the functional units.

Let’s take a closer look at what a server should consist of:

• The core of most backend applications is an HTTP server. It is a specialized part of the program that establishes communication with the outside world over the internet, receives requests from users, processes them, and returns responses.
• Often, the HTTP server comes bundled with a router in frameworks. This part of the application parses the request path and parameters, then passes the data to controllers for processing.

The router and the HTTP server form the foundation of your application. The choice of framework for routing requests determines how the entire server will operate.

• A controller is a module of the application that groups and encapsulates multiple routers operating on a specific resource: creating, reading, updating, and deleting it — these operations are known as CRUD. Controllers themselves do not contain business logic, but they play an important role in orchestrating processes such as routing, validation, data processing, and serialization.
• Services serve as the core of a server’s business logic and are generally organized into three primary categories: resource services, global internal services, and external services.
  • Resource services are specialized, local services associated with a single controller, responsible for managing the data and operations of a specific resource. For instance, a UserSevice is dedicated to handling operations for the User resource and can’t be used by other controllers.
  • Global internal services are services that encapsulate the logic for interacting with external systems owned by the server, such as databases, file storage, sockets, and many others.
  • External services are those required for the server’s operation but to which you do not have direct access. Examples include banking systems, email services, telecommunication providers, and similar third-party systems. They operate like global services but usually come with some kind of abstraction, allowing the provider to be changed if the need arises.

By dividing the server into distinct components and maintaining a clear hierarchy among them, we can achieve a modular architecture.

Need to add a new feature? Simply add a new controller. Need to upgrade business logic? Develop a new version of the service. Facing performance limitations? Before investing in costly optimizations, scale the existing server modules horizontally.

We at SWAN care deeply about architectural design to deliver the most scalable backend solutions tailored to our clients’ needs. To discover more about how we could help with your technology needs, contact us to schedule a free assessment.