Question 2: does exist some kind of optimization-per-usecase service for such a fixed cost scenario? E.g. "Optimize for Website" or "Optimize for Database" and you can download a Terraform file?
An example of this is s3 storage. You tend to find your storage cost will increase over time as you put more stuff into s3. S3 also charges per api call so you'd have to somehow fix that.
You have egress fess also which you're not in control of so variable customers usage will net a variable cost.
In terms of reserving compute power (a popular answer) you can also achieve fixed price with on demand if you don't auto scale. So reserving here doesn't remove that variability. Reserving just make it cheap if you have constant use. So you can reserve you DB server as it's always on and you'll save over on demand.
Many of the small cloud providers offer much less variability for their services with things like fixed networking cost. I tend to use those as I want a fairly fixed bill. The only thing that's variable on my cloud bill is backup storage and GBP to EUR exchange rate. The backup fee's are < 5% of the total cost at the moment.
AWS lets you provision some service though (I think DynamoDB has three different ways to be provisioned now) but it's not per use-case, it's based on what you think your needs are.
https://aws.amazon.com/ec2/pricing/reserved-instances/pricin...
2. You can chose which type of machine you want to reserve as your servers. Some of them are optimized for memory (good for databases). Some for CPU, etc