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Lambda REST architecture ​

The entire REST API is run by a single Lambda Function which parses the path and delegates to different handler functions. We do this because:

  • Each endpoint doesn't have to cold start independently.
  • It creates better separation between app logic and Pulumi logic.
  • It creates better separation between REST logic (matching paths, managing headers) and implementation logic for the endpoint itself.
  • It makes it easier to abstract "middleware" features like CORS

To learn more, take a look at the following code in the /infra/lib/lambda/rest directory:

  • Main.ts - This is the main lambda function and the entrypoint for all REST requests.
  • Router.ts - This file contains all the routing logic. Routes are defined at the bottom in the initRouter function.
  • CorsRules.ts - Provides a corsRules factory function for defining and applying CORS rules (allowed origins, etc.).
  • PathParser.ts - Matches paths (like /foo/123/bar/abc) to path patterns (like /foo/:foo/bar/:bar while extracting placeholder values into a result object (like {foo: '123', bar: 'abc'}).