Microservice architecture (MSA), due to its sheer power and distinct competencies continuously strengthens its beneficial footprint as the undisputed unit of agile application design, development, and deployment. MSA is evolving quickly with the continued contributions from scores of third-party tool and platform vendors. Computer scientists, IT professionals, and academic professors across the globe are bringing forth delectable advancements to make MSA groundbreaking and pervasive for the IT world. We have detailed this strategically sound application architecture pattern in other chapters. You can also find other chapters talking about the various contributions of MSA to be penetrative, participative, and pioneering.  In the following sections, we want to discuss the need for API gateway solutions and API management suites, and how they fulfill the goals of MSA goals with ease.

In a nutshell, an API Gateway is a proxy that has information about the main microservice endpoints. It mediates, routes, and invokes a respective endpoint after request verification, content filtering, authentication, and authorization. A functional view of an API Gateway is depicted next:

Typically, an enterprise-scale mission-critical application is composed out of hundreds of microservices. An API Gateway can help provide a unified entry point for external consumers, regardless of the number and composition of internal microservices. A typical API Gateway is being stuffed with the following competencies:

• Content Attack Prevention (CAP)
• Security policy configuration and enforcement
• API registration and publishing

• Routing and service mediation
• Traffic management and message throttling
• Monitoring of microservices to ensure the QoS attributes are meeting their targets

In short, an API Gateway provides a single and unified API entry point across one or more internal APIs. When a user enters an API Gateway, they may be coming from a variety of devices (web browsers or applications, mobile browsers or applications, and so on). They may expect structurally different responses. The AP gateway aggregates the requests from various client instruments and presents the aggregated one to the target service to facilitate the required processing.