Usually AWS is pretty good at hiding all the reliability and robustness that goes onto into making a customer's managed service. Customers are not made aware what it takes.
An interesting experiment would be doing the equivalent at the scale of the median saas company.
Setup mongodb (or any database) so that you have geographically distributed nodes with replication+whatever else and maintain the same SLA as one of the big hyperscalers. Blog about how long did it take to setup, how hard is it to maintain, and how much are the ongoing costs.
My hunch is a setup on the scale of the median saas company is way more simple and cost effective than you'd think.
