I see no reason you wouldn't be able to implement Datastore. In fact here's a public source claiming that Firestore (which I believe is its successor) is implemented on top of Spanner: https://www.theregister.co.uk/2017/10/04/google_backs_up_fir...
Also TBH now that I don't have commercial reasons to push interop, if I write another document database on top of FDB, I doubt I'd make it Mongo compatible. That API is gnarly.
Out of the many MongoDB criticisms, this one is valid. This https://www.linkedin.com/pulse/mongodb-frankenstein-monster-... article is quite right about it (note: endorsing the article does not mean I endorse its author by far).
Other than that, they totally did a fake it until you make it with MongoDB 3.4 passing Jepsen a year ago and MongoDB BI 2.0 containing their own SQL engine instead of wrapping PostgreSQL.
(I've tried to keep the above as dry as possible to avoid dragging the arguments around this situation into this thread - and I suspect the phrasing of the previous comment was also intended to try and avoid that, so let's see if we can keep it that way, please)
The Will Wilson I remember was not prone to such understatement. That API (and the corresponding semantics) was a nightmare.
I realized this 2 months ago at https://news.ycombinator.com/item?id=16386129
Congrats to the MongoDB team!
Too funny!
It's fast to install on a dev machine though, lol.
FoundationDB is now licensed under Apache 2, which is a much more permissive license, so most companies' open source policies allow it.
I know that multiple other companies have a similar policy (either a complete ban on using AGPL-licensed software, or special approval required to use it), although unlike Google, they don't post their internal policy publicly.
If someone works at one of these companies, what do you want to do – spend your day trying to argue to get the AGPL ban changed, or a special exception for your project; or do you just go with the non-AGPL alternative and get on with coding?
It is true that MongoDB's AGPL contagion and compliance burden, if you don't modify it, is less than many fear. It is also true that those corporate concerns are valid. MongoDB does sell commercial licenses so that such companies can handle their unavoidable MongoDB needs, but they would tend to minimize that usage.
It was a very bad rdbms (since they marketed as a replacement) and a very bad sharded db (marketed too).