Hello,
I have experience in developing Alexa skills:
Here is one I developed recently : [login to view URL]
Please take a look,
About wifi light switch, as you said it has API, I will be able to use it in alexa skill code, to turn light on/off . Yes, we can use lambda , or other server also we can use.
Please send me message, let's discuss details and confirm
Thanks,
Swapnil