APIkerros

APIkerros, often called the API layer in English, is the software layer that exposes application programming interfaces to external clients and internal consumers. It sits between clients (such as web apps, mobile apps, or partner systems) and the core business logic and data services. The APIkerros decouples client implementations from internal structures, allowing changes in the backend without breaking integrations.

Responsibilities include: request routing and protocol translation, authentication and authorization, input validation and data shaping, response formatting, versioning and deprecation, rate limiting, caching, logging and observability, and error translation.

Common patterns: API gateway acts as a centralized APIkerros component; a façade or aggregator wraps multiple services; in microservices, each service often has its own API layer; REST, GraphQL, and gRPC are common protocols; data formats include JSON and Protobuf; API governance includes documentation and developer portals.

Relationship to other layers: the APIkerros typically sits above the business logic layer and data access layer; it orchestrates calls to services, enforces contracts, and may implement cross-cutting concerns; it can also perform protocol translation and request aggregation.

Security and governance: uses OAuth 2.0, JWTs, API keys; CORS; auditing; versioning strategies; deprecation; monitoring.

In practice: widely used in web services and microservices architectures; enables partner integrations; necessary for scalability, security and evolvability.