how build an api?

Answer 1

Use php

Answer 2

Look at this, you can do it in 10 minutes (don't sue me later for that, it's the webpage's saying not mine) https://www.google.com.hk/url?sa=t&source=web&rct=j&url=https://readwrite.com/2015/11/16/how-to-build-an-api-amazon-lambda/&ved=2ahUKEwjp-Ljjpc3YAhUDtI8KHXL7AyQQFjAAegQICRAB&usg=AOvVaw0v06VHyDNa_SBBXTT8ug1i