> For the complete documentation index, see [llms.txt](/llms.txt).

# Onboard Users via USSD

Use USSD to interact with DeFi protocols on Rootstock.

- **Overview**: Learn how to build internet-free decentralized financial services on Rootstock using USSD, enabling P2P transfers and micro-loans on feature phones without internet access. [Read more](/use-cases/onboarding-ux/ussd-rootstock-defi/overview/)
- **Architecture & Data Flow**: Understand the complete USSD session lifecycle, relay server architecture, and how the Rootstock JSON-RPC layer connects feature phone interactions to on-chain smart contract execution. [Read more](/use-cases/onboarding-ux/ussd-rootstock-defi/architecture/)
- **Project Setup & Smart Contract Deployment**: Scaffold the USSD-Rootstock project using Hardhat 3, write the InclusiveDeFi smart contract, configure the Rootstock Testnet network, and deploy using Hardhat Ignition. [Read more](/use-cases/onboarding-ux/ussd-rootstock-defi/project-setup/)
- **Relay Server & Gateway Integration**: Build the Node.js Express relay server that bridges Africa's Talking USSD sessions to the InclusiveDeFi smart contract on Rootstock Testnet using ethers.js. [Read more](/use-cases/onboarding-ux/ussd-rootstock-defi/relay-server/)
- **Demo & Testing**: Validate the USSD-RSK bridge end-to-end using the Africa's Talking simulator and curl. Verify on-chain transactions via the Rootstock Testnet Explorer and understand current limitations. [Read more](/use-cases/onboarding-ux/ussd-rootstock-defi/demo-and-testing/)