Its also worth saying, at least in Mongo's case, AWS's managed offering (DocumentDB) is not, in any way except the API, MongoDB. Internally its based on Aurora.

Its also worth saying, at least in Mongo's case, AWS's managed offering (DocumentDB) is not, in any way except the API, MongoDB. Internally its based on Aurora. But, by my understanding, the SSPL also covers MongoDB's API, so this is why DocumentDB has not attained anything higher than 3.6 compatibility (and even its 3.6 compatibility is ish, but that's not for legal reasons by my understanding). Amazon definitely doesn't want to open source Aurora. Not only is it a massive moat for their cloud, its an extremely powerful database, but there's enough evidence to conclude that its so internal-AWS-reliant that it would be almost useless to anyone not running on AWS.