| Tool | Purpose | |------|---------| | | Error tracking and stack traces | | LogRocket | Session replay (see what user did before error) | | DataDog / New Relic | Performance monitoring, API latency | | Axiom / Grafana | Centralized logging | Example: Error logging with Sentry import * as Sentry from '@sentry/react'; Sentry.init( dsn: import.meta.env.VITE_SENTRY_DSN, environment: import.meta.env.MODE, tracesSampleRate: 0.1, // 10% of transactions );

src/ ├── features/ # Core business domains │ ├── auth/ # Login, logout, registration │ │ ├── components/ # Feature-specific UI │ │ ├── hooks/ # useAuth, useLogin │ │ ├── services/ # API calls for auth │ │ ├── types/ # TS interfaces │ │ └── index.ts # Public API of feature │ ├── dashboard/ │ └── products/ ├── shared/ # Reusable across features │ ├── ui/ # Buttons, modals, cards (pure components) │ ├── lib/ # Utilities, date formatters, validators │ ├── hooks/ # useLocalStorage, useDebounce │ └── api/ # Axios/fetch instance, interceptors ├── app/ # App-wide setup │ ├── store/ # Redux/Zustand store config │ ├── router/ # Route definitions │ ├── providers/ # Context providers wrapper │ └── styles/ # Global CSS, themes ├── main.tsx # Entry point └── vite.config.ts # Build tool config When you need to change "product logic," you open one folder. No jumping across 20 directories. 4. State Management Strategy Production apps require a layered state strategy :

path: '*', element: <NotFoundPage />, , ]);