lambdaweb4s is a lightweight library that bridges multiple AWS web integrations into single response/request model. The benefits of this approach are the following:

• convenient pattern matching syntax to map request to response objects
• zero dependency built-in development web server to test lambda locally
• lambda can be deployed in front of ALB or API Gateway without any change to source code

https://repo1.maven.org/maven2/io/github/markosski/lambdaweb4s_2.13/

Add lambdaweb4s dependency to your build system and create class that extends LambdaWebHandler. When deploying to AWS, configure your lambda function to be backed either by Application Load Balancer or API Gateway in passthrough mode. When executed locally, built-in web server will start up that you can use to test your application endpoints locally.

import lambdaweb4s.models.Methods._
import lambdaweb4s.LambdaWebHandler
import lambdaweb4s.DevWebServer
import lambdaweb4s.models._
import lambdaweb4s.models.Path.Root
import lambdaweb4s.models.Codes._

class Handler extends LambdaWebHandler {
  def accountInfo(accountId: String): Response = {
    Response.ok(s"Info for account: $accountId")     
  }

  def routes = {
    case GET -> Root => Response.ok("Hello World")
    case GET -> Root / "_health" => Response.ok("healthy")
    case GET -> Root / "accounts" / accountId / "info" => accountInfo(accountId)
    case _ => Response.text(NOT_FOUND, "page not found")
  }
}

object Handler extends App {
  val server = new DevWebServer(new Handler)
  server.listen(8080)
}

sbt "project example; run"

After building uber jar with build plugin of your choice you can run lambda app locally

java -jar application.jar