Let me clarify it for you.

Once you identified a solution that leads to your expected outcome, it's time to make it right. In the beginning you're validating what works and what doesn't, that means learning time is more important than scalibility. But after that, scalibility is what matters most.

It's a strategy, first build to learn, then build to last. And answering straight your question, the Sprint Goal could be, our solution supports 10x the users we have now, or Our code base matches our standards and it's maintainable.