The router-first approach to Single Page Application (SPA) architecture enables developers to start small with a decoupled and lazy-loaded architecture, giving them the option to stay small or scale while achieving sub-second first meaningful paints. Router-first architecture is designed to force teams to ask the hard questions early, build a roadmap and then iterate over a solution. In this session, Doguhan Uluca explores how router-first enforces high-level thinking, ensures consensus on features before coding starts, accounts for source code and team growth, and keeps engineering overhead low.