From this website:
Scalability is the ability to keep solving a problem as the size of the problem increases.
Scale is measured relative to your requirements. As long as you can scale enough to solve your problem then you have scale. If you can handle the number of objects and events required for your application then you can scale. It doesn’t really matter what the numbers are.
Scaling often creates a difference in kind for potential solutions. The solution you need to handle a small problem is not the same as you need to handle a large problem. If you incrementally try to evolve one into the other you can be in for a rude surprise, because it won’t work as you pass through different points of discontinuity.
Scale is not language or framework specific. It is a matter of approach and design.