In Microservice development, we mainly use a lot of interesting techniques and patterns. One of the interesting patterns in the microservice environment is called API Gateway. It describes a pattern for managing client requests for multiple services and offers a structured solution to various challenges in distributed systems and service-oriented architectures.
This article will help you understand the real value of an API gateway and will describe how to implement a simple API gateway in practice.
I always prefer to explain things in detail, let's say in theory, before implementing it in practice. The case here is that if you don’t have theoretical fundamental knowledge or an understanding of the thing, it doesn’t make too much sense to code it, and it is mostly not possible to get the most out of the implementation.
Let’s first answer the question: Why API Gateway?
In your microservice environment, the natural microservice-oriented design ends up with multiple microservices where all these services are separated and have their address to reach out to and invoke them. Using API Gateway, you don’t need to remember their address. API gateway acts as a Single Entry Point for such types of services. Instead of managing multiple endpoints for different services, our clients can now connect to one endpoint( to our API gateway), and it means we don’t need to keep track of multiple services’ addresses.
API Gateway service is a great place to implement our authentication, authorization, and SSL termination. Instead of implementing all these stuff for different services, now we can write them and manage them from one single point. As you might guess, API Gateway is a fundamental place to implement other cross-cutting concerns as well.
Can I implement logging in my API gateway? Of Course, it is a good design decision to implement one of the popular cross-cutting concerns called logging here. API Gateways can log requests and provide insights into usage patterns, performance, and errors. We can use this data not just for monitoring but also for improving our services.
When you have API Gateway, you can get responses from multiple services and aggregate them to provide only one single response to the client
You can implement data transformation inside your API Gateway. Data transformation logic here will act as an architectural decorator over you services.
Load balancing is another interesting functionality that you can integrate into your API gateway. Via Load Balancing, API gateways can distribute requests across multiple instances of a service, providing load balancing and improving systems’ scalability and resilience.
What if I want to add some limitations for calling the exact services? Well, that is also another interesting feature we implement inside the API gateway, and it is called Rate Limiting. Gateways can limit the number of requests from a client within a specific time frame. This prevents abuse and helps maintain performance levels.
Another must-have behavior for API Gateway is Fault tolerance. In our API Gateways, we can implement retries, circuit breaking, and timeouts. If a service is down or slow, the gateway can provide fallback mechanisms, improving overall resilience.
![API gateway]()
A small note: Although effective, the API Gateway pattern can introduce some overhead, such as an extra hop in communication and potential performance bottlenecks if not scaled properly. In simpler systems, a Backend-for-Frontend (BFF) pattern is sometimes preferred, where each client type has a dedicated gateway, reducing complexity for specific use cases.
Summary
As a pattern, the API Gateway provides a standardized way to handle client requests and manage cross-cutting concerns in a distributed system. It is a highly effective design pattern for microservices and complex applications that need centralized control and routing for multiple backend services.