Blockchain & Finance Lead — UEX.US Platform
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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 xpzdshu (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
* Intro call (30 min)
* Technical interview (Go + blockchain)
* Take-home (paid): ERC-20 indexer
* System design (custody + settlement)
* VP Engineering interview
* Offer (2–3 weeks total)