# Backend Integration

In production, the `CityFundClient` should live on your backend rather than in browser code. A thin server route keeps your API key private and gives you a natural hook for policy enforcement.

```
// server/fund.ts
import { CityFundClient } from "@cityprotocol/core";

const fundClient = new CityFundClient({
  apiKey: process.env.FUN_API_KEY!,
});

export async function handleDepositRequest(walletAddress: string, userId: string) {
  // 1. Run compliance checks against userId / walletAddress
  // 2. Enforce allowed-asset policy (e.g. stablecoins only)

  const uda = await fundClient.getUdaAddress({
    recipientAddr: walletAddress,
    userId: userId,
    network: "56",
    toNetwork: "56",
    toTokenAddress: "0x55d398326f99059fF775485246999027B3197955",
  });

  // 3. Log to your audit trail / reconciliation table
  return uda;
}
```

This pattern enables several production-grade capabilities: 

1. **allowed-asset policy** to restrict which tokens and networks your users can fund with, 
2. **compliance checks** to screen wallet addresses or user identities before generating a deposit address, 
3. **audit trails** to log every UDA generation event for internal reporting, 
4. **user mapping and reconciliation** to tie each deposit address back to your internal user records for downstream accounting.


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