If you're building for example an ecommerce that uses MongoDB as database, you're not selling MongoDB as a service, so you don't need to license your software with this new SSPL.
If you're building an ecommerce as a service with a MongoDB database, again you're not selling MongoDB as a service, so you're safe again.
IANAL + usual disclaimers.
From the SSPL:
13. Offering the Program as a Service.
If you make the functionality of the Program or a modified version available to third parties as a service, you must make the Service Source Code available via network download to everyone at no charge, under the terms of this License. Making the functionality of the Program or modified version available to third parties as a service includes, without limitation, enabling third parties to interact with the functionality of the Program or modified version remotely through a computer network, offering a service the value of which entirely or primarily derives from the value of the Program or modified version, or offering a service that accomplishes for users the primary purpose of the Program or modified version
“Service Source Code” means the Corresponding Source for the Program or the modified version, and the Corresponding Source for all programs that you use to make the Program or modified version available as a service, including, without limitation, management software, user interfaces, application program interfaces, automation software, monitoring software, backup software, storage software and hosting software, all such that a user could run an instance of the service using the Service Source Code you make available.
I've worked with some copyright lawyers that basically said "it's impossible to know, and we'd rather just avoid the question to begin with", and forbade us from using AGPL in any of our deployments.