But in my case I don't control the size of the input data
Not in production but you have an idea of both size and complexity and should be able to generate performance test scenarios, and related monitoring queries (system and service) to obtain some idea. The specifics are beyond my experience but this is not brand new technology and people have done similar stuff with it before.
And, as an extension to what you said, given such lack of control you are going to want to monitor performance in production anyway even with an assumed bullet-resistant solution.
David J.
