Over my career I've rarely seen anywhere with an "as live" environment that wasn't production. For that reason I don't particularly think this is a cloud only or even start up only DB problem.
I must be one of those rare exemptions.
when working on long term projects we used to have 3 envorinments.
1. QA, which was effectively "shared DEV". Worked like "throw it in and see what's happening".
Databases were copies from either Testing or Production, or sometimes special databases generated from a script.
2. Testing. Controlled environment. But still DEV hands allowed into it in certain circumstances.
In terms of code it was a copy of Prod plus approved changes from the VC system.
But the data were more than that. There were specially designed test cases which did not exist in production, but could appear there any time.
It was also exposed to the customer's, so they could make up accounts, submit trial orders, and so on.
our test Server was pretty ridiculous, which helped to identify the new code causing performance issues. 🙂 But the size of test databases was usually bigger, in some cases - times bigger than production. So we did not have surprises with degrading performance in Production.
3. Production. Well, Production. Controlled environment, DEV hands off, scripted deployments, data belongs to Customers.
You can perform stress tests at a far higher level than you would normally endure and shut it all down after an hour or so. Set up correctly this can be relatively inexpensive and more robust
I'm not sure what you mean by "stress test", but I don't think you can generate and put into database 3 years worth of data within an hour. With such a small database you may not to worry about any kind of scalability tests.