As for the most typical use case, web apps, see their FAQ:
> The copyleft condition of Section 13 of the SSPL applies only when you are offering the functionality of MongoDB, or modified versions of MongoDB, to third parties as a service. There is no copyleft condition for other SaaS applications that use MongoDB as a database.
https://www.mongodb.com/licensing/server-side-public-license...
Compare their prior, public clarification on the scope of AGPLv3:
> Note however that it is NOT required that applications using mongo be published. The copyleft applies only to the mongod and mongos database programs. This is why Mongo DB drivers are all licensed under an Apache license. You application, even though it talks to the database, is a separate program and “work”.
https://www.mongodb.com/blog/post/the-agpl
Much as Kernel developers published a statement clarifying and limiting the sweep of GPLv2 copyleft, Mongo published a statement clarifying and limiting the sweep of AGPLv3 copyleft.
I've heard from a former Mongo employee that Mongo wrote several letters to users and vendors, assuring them that AGPLv3 didn't require release of their app code.
Also, it's not like Amazon is not giving back to the open source community (https://aws.amazon.com/opensource/)