# Using your backend

Once the [SDK is set up](/build/sdk), every capability you configured is available through the
`foundation` instance. Each Configure page has a **Use in your app** section with the exact calls —
here's the map.

| Capability | In your app | SDK |
|---|---|---|
| [Authentication](/platform/auth#use-in-your-app) | Login, registration, sessions | `foundation.auth.*` |
| [Entities](/platform/entities#use-in-your-app) | Read and write your data | `foundation.db.*` |
| [Uploads & Files](/platform/uploads#use-in-your-app) | File uploads | `foundation.files.*` |
| [Billing](/platform/billing#use-in-your-app) | Plans, usage, gating | `foundation.account.*`, `foundation.config.plans` |
| [Integrations](/platform/integrations#use-in-your-app) | Connect services | `foundation.integration.*` |
| [Branding](/platform/apps#use-in-your-app) | App name, theme | `foundation.config.*` |

## Patterns that apply everywhere

- Handle **unauthenticated** users before calling authenticated services.
- Add **loading, empty, success, and error** states to every call.
- **Paginate** lists that can grow (`limit` + `cursor`).
- Read `foundation.config` for backend-provided theme, features, and plans instead of hard-coding them.

## Reference

- [SDK reference](/api/sdk)