Blockchain Engineer for On/Off-ramp Crypto Rails

I’m spearheading a new B2B payments rail that lets African businesses move seamlessly between crypto and local fiat. The immediate milestone is a production-grade, multi-chain wallet layer covering BTC, ETH, SOL and stable-coins such as USDT/USDC across ERC-20, TRC-20 and BEP-20. Web3.js/Ethers.js, Solidity or Rust will be your main playground because some smart-contract glue code and low-level services will emerge as we scale.

Core wallet requirements
• Cross-chain transactions that feel instantaneous to the end user
• True multi-currency balances under one address book
• Enhanced security: MPC architecture reinforced with two-factor authentication by default and biometric verification for high-value flows.

Beyond the wallet, you’ll own the crypto ↔ fiat on/off-ramp engine that settles into African bank rails and mobile-money corridors. That means orchestrating liquidity providers, swap routes and compliance hooks while keeping fees predictable.

Acceptance criteria
1. An audited MPC wallet service running in staging that signs and broadcasts mainnet transactions for all listed chains.
2. REST and WebSocket APIs exposing balance, send, receive and webhook callbacks documented via OpenAPI.
3. On-ramp that credits test fiat accounts within SLA <90 seconds; off-ramp payouts confirmed on-chain and in bank ledger within the same window.
4. Security suite passing penetration tests, including enforced 2FA and biometric triggers for transactions above configurable limits.
5. CI/CD pipeline (GitHub Actions) with unit, integration and E2E tests covering ≥90 % of critical paths.

If you’ve shipped wallet infrastructure before and enjoy piecing together Web3.js, Solidity or Rust micro-services, let’s talk about kicking this off for a 6-month full-time engagement starting immediately. Show More