MongoDB is very flexible and it is a blessing and a curse. It will store any data you provide. By default there is no validition you setup validation rules on database or use ODM like Mongoose if you're using NodeJs to help with validation in the application layer.
What is serverless ? Serveless is a service where you pay for how much compute power actually use, not how much you reserve. Why migrate? Migrate reasons can be several: from security, to cost
Service Level Indicator (SLI) measure of chosen characteristic of the level of service.
Assign only those permissions which are required to get the job done. Also utilise infrastructure as a code (IaC) tool like Terraform to track changes in your infrastructure to prevent unwanted human error and if it happens track down easily.
Micro services is a fun in itself. Here are tips when to use messaging over direct HTTP communication. When to use HTTP: Need to message service directly Requires a confirmation about success or