Flowsend

FlowSend is a gasless, bank-integrated stablecoin remittance platform built on Base that makes sending and receiving USD as simple as sending a text message. It hides blockchain complexity (wallets, gas, chains) behind smart wallets and a familiar fintech UX while using USDC on Base as the settlement rail and Circle for regulated fiat on/off-ramps.

We built FlowSend using a combination of Base, OnchainKit, and Coinbase Wallet SDK to enable frictionless, cross-border money transfers that abstract away blockchain complexities for everyday users.

The frontend is built with Next.js, React, and TypeScript, styled with Tailwind CSS for responsiveness and a clean UI. The backend runs on Node.js with Express, handling off-chain data persistence and API coordination. We used Base as the underlying blockchain for fast and low-cost transactions, while OnchainKit provided composable hooks and utilities to simplify onchain interactions — including wallet connection, transaction management, and account abstraction.

Transfers are executed using gasless meta-transactions, where users sign messages that are relayed and paid for by our backend relayer, eliminating the need for users to hold crypto for gas. The backend integrates with Coinbase Wallet SDK and Base Paymaster services to handle gas sponsorships securely.

For fiat integration, we connected a lightweight payment layer that links traditional banking APIs to onchain transfers, allowing users to send or receive money seamlessly, whether onchain or offchain.

A particularly hacky part was implementing hybrid transaction routing, we detect whether a recipient has an onchain address or not; if they don’t, we generate a temporary wallet using account abstraction and notify them via email or SMS. Once they claim the wallet, the funds are released automatically.

Overall, FlowSend bridges traditional banking UX with onchain efficiency, offering a smooth, instant, and gasless payment experience built entirely on Base.