Blockchain & Finance Lead — UEX.US Platform
Location: Madrid, Spain (Hybrid — 3 days onsite)
Company: Quanta Tech Systems Europe (US-backed, Quanta Tech Systems LLC)
Employment: Full-time, permanent (Spanish contract)
Salary: €70,000 – €95,000 + bonus + token allocation
About Us
Quanta Tech Systems Europe is building the core infrastructure behind UEX.US — a next-generation, U.S.-regulated digital asset exchange (Wyoming, est. 2025).
Our platform combines:
- Crypto trading
- Staking & yield products
- Crypto-backed lending
- Tokenized real-world assets (gold, silver, equities)
We are scaling our Madrid HQ and looking for a Senior Blockchain & Fintech Engineer to take ownership of the most critical layer — where code meets real money movement.
Your Mission
You will be the technical anchor for blockchain and financial systems:
- On-chain settlement
- Wallet & custody infrastructure
- Exchange core (matching, ledger, reconciliation)
- Fiat ↔ crypto rails
This is a high-impact role — your systems will directly move and secure real assets.
What You’ll Do Blockchain Engineering
- Build Go services interacting with:
- EVM chains (Ethereum, Polygon, Arbitrum, Base)
- Non-EVM (Bitcoin, Solana, XRP, Cardano)
- Own wallet infrastructure:
- HD wallets (BIP-32/39/44)
- HSM / MPC integrations
- Hot / warm / cold architecture
- Develop:
- Indexers & reorg-safe pipelines
- Gas optimization tools
- Integrate custody providers:
- Fireblocks, Copper, BitGo
- Review smart contracts & define listing security standards
Finance & Exchange Systems
- Work on:
- Order book & matching engine
- Ledger & settlement systems
- Ensure:
- Double-entry accounting
- Idempotency
- Cross-chain reconciliation
- Build fiat integrations:
- PayPal, Zelle, Apple Pay, cards
- Implement:
- Crypto-backed loans
- Staking rewards
- APY-based savings
Leadership & Ownership
- Act as domain tech lead (blockchain + finance)
- Define:
- Engineering standards
- Observability & incident response
- Mentor engineers & support hiring
- Drive architecture via RFCs
Must-Have
- Go (Golang) — 4+ years in production systems
- Blockchain/Web3 — 2+ years (Ethereum or similar)
- Strong understanding of:
- Transactions, gas, nonce, reorgs
- Cryptography (ECDSA, keccak)
- Fintech experience :
- Exchanges / payments / ledger systems
- Distributed systems :
- Kafka, PostgreSQL, Redis
- Cloud & Infra :
- AWS, Docker, Kubernetes, CI/CD
- Security mindset :
- Key management, attack vectors, front-running
- Claude Code (required) :
- Daily usage
- AI-assisted workflows
- English — professional level
Nice to Have
- Solidity / Rust
- Experience in:
- Crypto exchange / neobank
- Regulatory knowledge:
- MiCA / FinCEN / SEC
- MPC / HSM (CloudHSM, Vault, etc.)
- Open-source contributions (geth, Bitcoin Core, etc.)
- RWA (tokenized assets) experience
Tech Stack
Languages: Go, TypeScript, Solidity, Rust
Chains: Ethereum, Polygon, Bitcoin, Solana, XRP, Cardano
Data: PostgreSQL, Redis, Kafka, ClickHouse
Infra: AWS, Kubernetes (EKS), Terraform
Security: Vault, AWS KMS, Fireblocks, Chainalysis
Observability: Prometheus, Grafana, OpenTelemetry
AI: Claude Code, Claude Opus 4.7
Compensation & Benefits
- €70k – €95k salary
- Bonus up to 15%
- Token allocation (vesting)
- MacBook / Linux workstation + €2,000 setup
- €2,500 learning budget (Devcon, EthCC, Money20/20)
- Private health insurance (Sanitas / Adeslas)
- 25 vacation days + holidays
- ✈️ Travel (NYC, London, Paris, Brussels)
- Relocation support + visa
Hiring Process
1. Intro call (30 min)
2. Technical interview (Go + blockchain)
3. Take-home (paid): ERC-20 indexer
4. System design (custody + settlement)
5. VP Engineering interview
6. Offer (2–3 weeks total)