What do the page response times look like, since it seems like the included php opcache wouldn’t function, nor would user data caches like apcu?
Yes, PHP opcache and optimizations don't work since it gets cold started every time.
[1] Pingdom speed test results: https://i.imgur.com/9zg9l3g.png
Seems like other people have had this idea in the past too!
https://forums.aws.amazon.com/message.jspa?messageID=624889
Are there any workarounds allowing something similar?
https://s3.amazonaws.com/sanchit-uploads/guestbook.txt
It looks like some Russian bots found your input. I know it's just a demo, but might want to add at least a honeypot on there or something.
Anyway, this is pretty slick and snappy. Neat idea.