Blockchain & Smart Contract Engineer
5 hours ago
Bilbao
pbAbout the role /b /ppbr/ppWe are seeking a bSenior Blockchain Backend Engineer /b to help maintain and evolve bDebita by Neitec /b, our on-chain asset-based private credit infrastructure. This role combines production smart contract engineering with backend integration work across Web3 infrastructure, payment rails, custody providers and off-chain financial systems. /ppbr/ppThe ideal candidate has already deployed and maintained smart contracts handling real-world capital, understands the full lifecycle from testnet to mainnet, and is comfortable building the backend services required to connect on-chain financial logic with APIs, databases, wallets and settlement flows. /ppbr/ppbRequirements /b /ppbr/pulliFluent Spanish is required, as the role involves working closely with Spanish-speaking teams and stakeholders. /liliThe candidate must be based in Spain, preferably in Madrid, or willing to work within the Spanish time zone. /li /ulpbr/ppThis is NOT a junior position. We need someone who has: /ppbr/pulliDeployed and maintained smart contracts handling real-world capital in production /liliExperienced the full lifecycle of blockchain projects from testnet to mainnet /liliDebugged critical production issues under pressure /liliMade architectural decisions that impact security and scalability /li /ulpbr/ppKey distinction: You'll split your time 50/50 between: /ppbr/pulliSmart Contracts SDK Layer (EVM, Solidity, TypeScript SDK) /liliAPI Integration Layer (Backend services consuming Web3 infrastructure) /li /ulpbr/ppbCore responsibilities /b /ppbr/ppb1. Smart contract development maintenance (50%) /b /ppbr/ppProduction contract management /ppbr/pulliMaintain and upgrade existing bond issuance contracts /liliDeploy new bond instances to mainnet following strict security protocols /liliMonitor on-chain operations and respond to incidents /liliCoordinate with auditors for security reviews before major upgrades /li /ulpbr/ppFinancial logic implementation /ppbr/pulliImplement complex amortization schedules (French, bullet, hybrid models) /liliDesign settlement mechanisms (atomic on-chain vs hybrid off-chain) /liliBuild compliance enforcement at the smart contract level (KYC/AML whitelisting) /liliIntegrate with Chainlink Automation for scheduled operations (interest payments, redemptions) /li /ulpbr/ppSDK development /ppbr/pulliMaintain TypeScript SDK used by API /liliGenerate and version ABIs, TypeChain bindings, and contract interfaces /liliWrite integration tests ensuring SDK behavior matches contract state /liliDocument breaking changes and coordinate releases with API team /li /ulpbr/ppb2. Web3 API integration (50%) /b /ppbr/ppBackend services /ppbr/pulliIntegrate SDK into NestJS API services /liliBuild reliable transaction management (nonce handling, gas estimation, retry logic) /liliDesign off-chain balance registries synchronized with on-chain state /li /ulpbr/ppPayment rails custody integrations /ppbr/pulliIntegrate with fiat on/off ramp providers (bank accounts, payment processors) /liliConnect payment rails: crypto transfers, SEPA, ACH and local payment methods /liliIntegrate with liquidity providers and custody solutions (MPC wallets, institutional custodians) /liliBuild synchronization mechanisms between on-chain state and off-chain legacy systems /liliCoordinate atomic or hybrid DVP (Delivery vs Payment) settlements across chains and rails /liliHandle wallet management, signing flows, and key rotation strategies /liliImplement transaction batching and gas optimization at API level /li /ulpbr/ppbTechnical requirements /b /ppbr/ppbBlockchain / Smart Contracts /b /ppbr/ppProduction solidity experience /ppbr/pulli2+ years writing production Solidity /liliDeployed contracts managing real fundson mainnet /liliHandled production incidents (reverted transactions, gas spikes, oracle failures) /liliExperience with upgradeable contracts (UUPS, Transparent, or Beacon proxies) /liliDeep understanding of EVM internals (storage layout, gas optimization, assembly when necessary) /li /ulpbr/ppConcrete skills /ppbr/pulliWrite gas-efficient Solidity following best practices /liliDebug failed transactions using Tenderly, block explorers, or local forking /liliPerform upgrades on live contracts without downtime or data loss /liliImplement custom error handling, events, and role-based access control (OpenZeppelin) /liliUnderstand reentrancy risks, front-running, and common attack vectors /li /ulpbr/ppTools frameworks /ppbr/pulliFoundry(primary) or Hardhat (legacy support) /liliOpenZeppelin Contracts (v5.x upgradeable suite) /liliChainlink Automation (keeper-compatible contracts) /li /ulpbr/ppbBackend development /b /ppbr/ppTypeScript/Node.js /ppbr/pulli3+ years building production Node.js services /liliExperience with NestJS or similar enterprise frameworks /liliProficient in ethers.js v6 (contract interactions, wallet management, event parsing) /liliAsync/await patterns, error handling, and retry mechanisms /li /ulpbr/ppDatabase state management /ppbr/pulliPostgreSQL for off-chain data (transactions, balances, audit logs) /liliUnderstanding of eventual consistency in blockchain-to-database sync /liliExperience with migration scripts and schema versioning /li /ulpbr/ppAPI design /ppbr/pulliRESTful API design for financial operations (idempotency, validation) /liliWebSocket streams for real-time blockchain events /liliRate limiting and authentication for sensitive endpoints /liliError handling that doesn't leak private keys or internal state /li /ulpbr/ppbIntegration traditional finance /b /ppbr/ppBridge blockchain with legacy systems /ppbr/pulliExperience integrating blockchain with traditional banking/payment infrastructure /liliUnderstanding of fiat on/off ramps(convert crypto fiat via bank accounts) /liliKnowledge of payment rails:SEPA (Europe), ACH (US), wire transfers, local payment methods (SPEI/Mexico, Pix/Brazil, FedNow, etc.) /liliBank account integration experience (APIs for deposits, withdrawals, reconciliation) /liliCustody provider integrations (MPC wallets, institutional custodians, key management services) /liliLiquidity provider coordination (ensuring sufficient funds for settlements) /li /ulpbr/ppOn-Chain / Off-Chain state synchronization /ppbr/pulliDesign systems that maintain consistency between blockchain state and database state /liliHandle eventual consistency and reconciliation between on-chain events and off-chain records /liliBuild idempotent operations that can safely retry without double-spending or data corruption /liliMonitor and alert on synchronization drift (on-chain balance ≠ database balance) /li /ulpbr/ppDelivery vs Payment (DVP) coordination /ppbr/pulliAtomic DVP: On-chain smart contract settlement (payment + delivery in single transaction) /liliHybrid DVP: Coordinate on-chain delivery with off-chain payment (via bank transfer, custody ledger) /liliHandle multi-leg settlement flows (bond issuance → fiat payment confirmation → token delivery) /liliImplement rollback/refund logic when one leg of DVP fails /liliExperience with escrow mechanisms, multi-signature approvals, or atomic swaps /li /ulpbr/ppbConcrete skills /b /ppbr/pulliIntegrate with payment processor APIs /liliHandle currency conversion and multi-currency accounting /liliDesign webhooks and callbacks for asynchronous payment confirmation /liliUnderstand regulatory requirements for AML/KYC in payment flows /li /ulpbr/ppbFinancial protocols understanding /b /ppbr/ppCapital markets basics /ppbr/pulliBond lifecycle: issuance → coupon payments → principal redemption → maturity/default /liliAtomic DVP (fully on-chain: smart contract ensures simultaneous delivery + payment) /liliHybrid DVP (on-chain delivery coordinated with off-chain payment via bank transfer or custody ledger) /liliEscrow and multi-signature approval flows /liliAmortization schedules /liliRoles management /li /ulpbr/ppTokenization concepts /ppbr/pulliSecurity token standards (ERC-20 with compliance hooks) /liliOn-chain vs off-chain compliance (hybrid models) /liliCustodial vs non-custodial wallets in institutional context /li /ulpbr/ppbNice-to-have experience /b /ppbr/ppAdvanced blockchain /ppbr/pulliMulti-chain deployments (experience with 2+ EVM chains in production) /liliMEV awareness and mitigation strategies (private mempools, Flashbots) /liliGas optimization at scale (batch operations, signature aggregation) /liliExperience with account abstraction (ERC-4337) or smart contract wallets /li /ulpbr/ppDomain experience /ppbr/pulliBuilt or maintained aReal-World Asset (RWA) protocol /liliExperience withSecurity Token standards (ERC-3643, ERC-1400) /liliWorked unregulated fintech (securities, payments, custody) /liliIntegrated with institutional custody /li /ul