How API Gateways Simplify Client Access in Microservice‑Based Online Stores

Background

When building an online store with a microservice architecture, the product‑detail page must gather information from several services, such as product info, pricing, orders, inventory, and comments. The UI must be provided for both HTML5/JavaScript browsers and native Android/iOS clients, and the store must expose product details via a REST API for third‑party use.

Problem

How can client applications in a microservice architecture access the various services?

Requirements

Microservice APIs are often more fine‑grained than what a client needs, requiring aggregation across multiple services.

Different clients need different data; for example, desktop browsers usually need richer detail than mobile browsers.

Network performance varies: mobile networks are slower and higher latency than LAN connections used by server‑side web apps, limiting the number of requests a mobile client can make.

Service instance counts and locations (host/port) change dynamically.

The way services are partitioned may evolve over time and should be invisible to the client.

Solution

Introduce an API gateway as a single entry point for all clients. The gateway either proxies requests directly to the appropriate service or aggregates data from multiple services before responding.

Unlike providing a one‑size‑fits‑all API, the gateway can expose client‑specific APIs; for instance, Netflix’s API gateway runs client‑specific adaptation code to deliver the most suitable API for each client. The gateway can also enforce security, such as validating client permissions.

Example

Netflix API Gateway

Result

The API gateway offers several advantages:

Clients remain unaware of how the application is split into multiple microservices.

Clients are insulated from the physical location of service instances.

Each client receives an optimal API.

Reduces request/round‑trip count; the gateway can retrieve data from multiple services in a single round‑trip, lowering load and improving user experience, especially for mobile apps.

Simplifies client logic by moving multi‑service calls to the gateway.

Drawbacks include:

Increased complexity, as the gateway itself must be developed, deployed, and managed.

Potential extra network hop, adding latency, though usually negligible for most applications.

Open Question

How to implement an API gateway that can scale for high load? Event‑driven or reactive solutions (e.g., Netty, Spring Reactor on the JVM, or Node.js) are ideal choices.

Related Patterns

Microservice architecture creates the need for an API gateway.

The gateway must use client‑side or server‑side discovery to route requests to available service instances.

Known Use Cases

Netflix API Gateway

References

Original English article: http://microservices.io/patterns/apigateway.html

Reposted at: http://blog.csdn.net/xn_sung/article/details/52318969