✓ GOOD: Functional Grouping Parallel-safe. One team per epic. Epic A: Core Authentication User Model JWT Service Login Endpoint Password Reset W1: User Model W2: JWT + Login W3: Password Reset Epic B: Notification System Email Templates Notif Service Event Handlers blocks Wave Execution Wave 1: User Model + Email Templates ← parallel Wave 2: JWT Service + Notif Service ← parallel Wave 3: Remaining (parallel) 3 waves. Maximum parallelism. ✗ BAD: Layer Grouping Forces serial. Cross-epic spaghetti. Epic X: Database Layer User Tbl Session Notif Tbl Epic Y: API Layer Auth Ctrl Middleware Notif Ctrl Epic Z: Frontend Login Pg Dashbrd Notif Pnl Wave Execution Wave 1: Database Layer only ← blocked Wave 2: API Layer (waits for Wave 1) ← blocked Wave 3: Frontend (waits for Wave 2) ← blocked 3 waves but ZERO parallelism. Pure serial.