React Performance: Async Waterfall — Defer Await. Keywords: async await defer branch. Platform: React/Next.js. Description: Move await into branches where actually used to avoid blocking unused code paths. Do: Move await operations into branches where they're needed. Don't: Await at top of function blocking all branches. Good Example: if (skip) return { skipped: true }; const data = await fetch(). Bad Example: const data = await fetch(); if (skip) return { skipped: true }. Severity: Critical.