The backend of the alphanumeric string retrieval example follows established ExpressJS patterns and does not deviate much. The backend itself is written in TypeScript, as I believe that node APIs benefit greatly from establishing data structures and maintaining type safety throughout.
A configuration file is put in place to allow for the application to behave differently if run in development, staging, testing, or production modes.
The application is bootstrapped in src/app.ts, which in turn initiates the application routes, found in src/routes.ts. The routes each call a controller, which handles the routing and determines the response of various calls to the API.
A basic ErrorLog and Log are established will log all incoming requests (except for GET and OPTIONS, as those are typically unnecessary for logging, except for the case of debugging performance problems). The important route, found in src/controllers/alpha.ts simply returns the requested string immediately.
Controller route functions all call the next() parameter, which will pass errors to a global error handler, found in server.ts. This will log all uncaught exceptions, and can be used for future debugging.