Yep! I'm really starting to like this Lambda + S3 pattern for one-off sites like this, it's so much cheaper and easier than setting up RDS. I just use S3 as a dumb Key Value store literally by reading in and out JSON files. From Lambda with small files, it's quite fast.

You can see an example of this in the source for Zappa BitTorrent Tracker, which has the option of either using S3 or DynamoDB: https://github.com/Miserlou/zappa-bittorrent-tracker

You can also look at the KEV Project, which uses the same idea with a bit more finesse: https://github.com/kevproject/kev

It actually builds a whole ORM on top of that pattern, and can optionally use Redis in tandem with S3.