Scaling Evolution

Grow a design one bottleneck at a time. A system that serves 1k users and one that serves 10M users are different architectures, but you do not jump between them — you walk a path where each step removes the current ceiling and exposes the next. Getting this wrong means either over-building day one (paying multi- region complexity for 1k users) or freezing when load doubles because the design was a memorized end-state, not a sequence of justified moves (GUIDE #7).

When to reach for this

A load increase is on the table ("what if traffic 10×?", "scale to millions"), the user asks where the bottleneck is or what breaks first, or a single-box design has outgrown one machine. Reach here to sequence the next two or three moves — never the whole roadmap at once.