> ## Documentation Index
> Fetch the complete documentation index at: https://docs.4mica.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Backend

> Use 4Mica backend SDKs and middleware.

# Backend

Backend integrations protect resources and coordinate settlement. Use backend middleware when you are the seller, and direct SDK operations when you need wallet, collateral, or operator-facing actions.

## TypeScript

Use <code>@4mica/x402</code> for Express middleware and server-side 4Mica x402 support. It wires protected routes, guarantee verification, facilitator calls, and scheme registration.

## Python

Use <code>4mica-x402</code> for FastAPI or Flask middleware. Use <code>sdk-4mica</code> for collateral management, balances, and on-chain operations.

## Rust

Use <code>sdk-4mica</code> for collateral and wallet operations. HTTP server middleware is planned, so use TypeScript or Python when you need production x402 middleware today.