What is the role of API gateway in microservices architecture?
Microservices have become the favored architecture for modern software applications over the traditional monolithic approach. This shift is primarily due to the need to handle complex functionalities requiring multiple services to work together flexibly. A microservice architecture makes applications more manageable and easier to develop, offering enhanced modularity compared to monolithic systems.
When a client application needs to interact with multiple microservices simultaneously, the usual approach involves making individual API calls to each microservice. Unfortunately, this can lead to increased resource consumption, reduced performance, and longer task times. To address these challenges, an API gateway is a central entry point for all API requests. Positioned between the microservices and clients, it acts as a gateway, streamlining communication and improving overall efficiency.
The API gateway is an intermediary between the client and microservices and does the following:
Authentication and authorization: Only the authenticated and authorized API calls can access the resources of microservices. The API gateway can act as an extra security layer by handling authentications and authorization of incoming requests. This ensures that only authorized requests can access microservices and their functionalities.
Load balancing and routing: The API gateway directs client requests to the suitable microservices according to the requested endpoints. It efficiently manages load balancing and evenly distributes incoming traffic among the various service instances, simplifying the process for clients and ensuring optimal performance. For example, a request from a client related to processing an order is forwarded to the following three services:
User service authenticates the user before processing the order.
The payment service is responsible for handling online payments.
The order service maintains records and statuses of orders.
Composite API calls: If a client needs to communicate with multiple microservices simultaneously, the API gateway receives the client's call and efficiently directs them to the relevant microservices by processing the parameters in composite API calls. It then collects the microservices' responses and sends a consolidated response back to the client, effectively handling their requests. The above illustration also indicates how a composite call is directed to multiple services.
Protocol translation: The microservice might be accessed by different clients. The API gateway can perform protocol translations, enabling clients to communicate using different protocols, while internally, the microservices can continue using their preferred communication protocols. This flexibility ensures seamless interactions between clients and microservices, regardless of their communication requirements.
Caching: The API gateway caches responses from microservices and improves the overall load on the back-end services by responding directly from the cache.
In summary, the API gateway streamlines the interactions between clients and microservices, providing a unified interface and handling specific crosscutting concerns. As a result, it improves the overall maintainability and scalability of the microservice architecture.
