Summary
Scalability is sometimes called a "non-functional requirement," implying that it is unrelated to functionality, and strongly implying that it is less important. Nothing could be further from the truth. Rather, I would say, scalability is a prerequisite to functionality - a "priority-0" requirement, if ever there was one.
I hope that you find the descriptions of these best practices useful, and that they help you to think in a new way about your own systems, whatever their scale.
