KosmoJS's API layer is built on Koa, leveraging its elegant middleware composition model and powerful context object to create a clean, extensible foundation for API development.

🏗️ Built on Koa

Koa's minimalist design provides just enough structure without imposing unnecessary abstractions. Its async/await approach makes asynchronous code natural to write and reason about, while the context object provides a clean way to pass request-scoped data through middleware chains.

The middleware composition pattern - where each piece can modify the request, delegate to the next middleware, and then modify the response on the way back - creates predictable, testable request handling pipelines. (Details)

🛡️ Type Safety Throughout

KosmoJS extends Koa's foundation with type safety throughout the request-response cycle. You define your API contracts in TypeScript types - parameters, payloads, responses - and these types flow through to runtime validation automatically.

There's no context switching between writing schemas in one DSL and implementing logic in another language. Everything lives in TypeScript, in the same file, maintaining a cohesive development experience. (Details)

🔧 Structured Yet Flexible

The defineRoute function provides structure for organizing HTTP method handlers while preserving Koa's flexibility.

Veterans will recognize the familiar elegance of KosmoJS's HTTP methods mapper, which draw inspiration from Sinatra framework - the Ruby framework that pioneered minimalist web development back in 2007.

The use function enables fine-grained middleware control at the route level, complementing global middleware with route-specific behavior. (Details)

Context and state extensibility means middleware can augment requests with authentication details, database connections, or any other request-scoped data, all with proper TypeScript types that flow through your entire handler chain.

This approach creates APIs that are both type-safe and pragmatic - you get compile-time checking and runtime validation without sacrificing the flexibility to handle real-world requirements that don't fit neat abstractions.