Architecture Fundamentals

Architecture is the set of decisions that are expensive to change — which components exist, where their boundaries are, which direction dependencies point, how data and failures move between them — and the skill is choosing the simplest structure that meets a measured requirement.

A system grows from browser → backend → database into gateways, services and caches one measured problem at a time — CPU at 90%, p99 above 800 ms, four teams blocked on one deploy — and every step buys capacity by adding a problem you did not have before.