RampLock

What I built: RampLock is a provably safe crypto to Naira off ramp on Monad. Users connect their wallet, lock MON against a backend signed quote, and receive Naira in their bank account through Monnify. Their MON remains locked in an escrow contract until fiat settlement is verified. If the payout fails, they can reclaim their MON onchain. The system consists of three components: a Solidity escrow contract on Monad Testnet, a NestJS backend that signs EIP 712 quotes, processes Monnify payouts, listens for contract events, and verifies webhooks, and a Next.js frontend that reads escrow state directly from the blockchain. What problem it solves: Off-ramping crypto in Nigeria often requires trusting exchanges or P2P merchants after already giving up your crypto. RampLock removes that risk. Instead of hoping a payout arrives, users lock MON in escrow. The funds are released only after a verified bank transfer. If settlement fails, they recover their crypto. The user is never worse off than before they locked their assets. What I learned: The biggest lesson was to verify assumptions instead of trusting documentation. I discovered API limitations, incorrect webhook documentation, and RPC constraints that only appeared in real integrations. I also learned that designing around a single invariant, MON never leaves escrow until fiat settlement is confirmed, simplified every architectural decision, from the smart contract to backend verification. Finally, I learned the importance of being transparent. The escrow runs on Monad Testnet, the Monnify integration uses signed sandbox APIs, and no real Naira moves during the demo.