Summary
Both Dockerfile and Dockerfile.ECS.Alpha refer to using npm start which in turn executes this script:
  "scripts": {
    "build": "tsc -p tsconfig.json",
    "start": "nodemon --watch 'src/**/*.ts' --exec 'ts-node' src/index.ts"
  }
 
Here, usage of both --watch and ts-node add extra overhead as there should be no requirement of ts-node and or watch.
As per this thread How to use ts-node in production, we should either use --transpile-only or even better have a prebuild step that precompiles all the typescript code into javascript. This will reduce the extra overhead ts-node and watch adds.