Microservice is a modern architectural style of developing software systems; that structures an application as a collection of smaller independent services. Doing so allows the services to be independent, highly maintainable, easy to scale and loosely connected via APIs.
What Is an API Gateway?
An API gateway is a tool situated in front of the APIs, which can serve as a single point of contact for all API consumers i.e. internal as well as external users. The gateway enforces security policies to protect against threats, and efficiently routes traffic between API producers and consumers.
An API gateway works by receiving API requests from a client, aggregating multiple requests, and routing them to the required services. Similarly when responses are received, the API gateway aggregates them and routes them back to the user.
Modern cloud native applications based on a microservices architecture utilize API gateways to maintain resilience and fast performance. Microservices based applications consist of autonomous, independent, single-function components making them easy to deploy, maintain and test each microservice independently.
Key capabilities of API gateways
1. API Security:
Access control is a major driver for the adoption of API gateway technology. An API gateway must provide an authentication layer so that only authenticated users can access a backend API. It should also be able to integrate with existing authentication providers, such as API keys, JSON web tokens (JWT), lightweight directory access protocol (LDAP), OAuth, OpenID Connect (OIDC), and custom services.
Once an account is authenticated, the API gateway authorizes the targets it is allowed to access. An API gateway should also support authorization—this means it should be able to abstract the structure of backend APIs and control user access to specific functions, data, or operations. An API gateway must be able to leverage existing authorization mechanisms such as role based access control (RBAC).
2. Rate-Limiting:
API gateway reduces load on back-end APIs and helps prevent abuse. Rate limiting limits access to the API, only allowing a certain number of requests per period, user, or group of users. Rate limiting makes it possible to maintain stable performance and to expose APIs safely to third-party consumers, creating new revenue opportunities.
3. API Monitoring and Logging:
An API gateway should provide basic monitoring for all APIs and be able to track requests, response times, and service level agreements (SLAs). The API gateway should also provide unified logging for all APIs. Logs should include a request ID, which makes it possible to correlate request headers with API activities, to enable end-to-end debugging.
4. API Transformation:
An API gateway must provide the ability to transform request and response payloads. Payload transformation can support organizations moving from traditional SOAP-based architectures to modern REST-based API architectures, and can help accelerate time to market.
How API Gateways can help with microservices challenges:
Handling microservice requests:
Microservices enables product teams to easily develop, deploy, and maintain different application functions, but they also make it difficult for external users to quickly and securely access the application. An API gateway helps solve this issue. Instead of asking customers to request access to each microservice separately, the gateway provides a single point of entry for all requests.
Once a request for information comes into a microservices-based application, the API gateway retrieves and returns the data, streamlining this process. It sends them to the relevant service, collects results, and sends them back to the customer. The gateway handles access control and also allows reliable and fast delivery in large, complex applications.
Routing application traffic:
An API gateway provides a management interface for many important aspects of the application. It serves as the main proxy that connects customers to services, supporting security and administration functions such as metric collection, authentication, response transformation, and input validation.
Each microservice runs in an independent environment, allowing you to add, upgrade, move and change them without affecting the overall application. API gateways enable you to easily route traffic and scale up microservices applications.
Conclusion:
API management can enable product teams to manage the entire API lifecycle. They can use API management tools to manage how APIs are published and shared with developers and partners, and control who can access each API. The API gateway also handles access control and also allows reliable and fast delivery in complex SaaS applications using multiple microservices.
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