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# Backend Engineer

- **Company:** Yei Finance
- **Location:** Madrid, Spain (Remote available)
- **Salary:** €70,000.0 - €90,000.0
- **Contract:** Permanent contract
- **Skills:** Agile Methodology, Business Logic, Programming Tools, Distributed Systems, Monitoring of Systems, Python (Programming Language), Open Source Technology, Systems Architecture, Backend, Solidity, Web3.js, Vulnerability Analysis, Golang
- **Published:** July 20, 2026
- **Apply:** https://www.adzuna.es/contact-us.html

## About the Role

+ Startup-Oriented: Comfortable operating in fast-moving, ambiguous environments and taking ownership from day one.
 + Mission-Driven: Motivated by building innovative DeFi products.
 + Collaborative: Communicates clearly and works effectively across both synchronous and asynchronous teams.
 + Product-Quality Focused: Cares deeply about user experience and the details that make a product exceptional.
 + Autonomous: Able to manage your own time, priorities, and outcomes in a fully remote setup., + 3+ years of smart contract development experience in Solidity, including familiarity with OpenZeppelin standards, Mainnet deployments, and audit collaboration
 + Proficiency in Golang or Python, with a proven track record in developing high-concurrency or distributed systems
 + Deep understanding of the mathematical models and business logic behind DeFi protocols (lending, AMMs, or derivatives)
 + Mastery of development tools: Hardhat / Foundry and related testing frameworks
 + Solid grasp of EVM internals, storage, memory, gas, and transaction lifecycle
Nice-to-haves:

 + Experience with cross-chain messaging protocols (LayerZero, Wormhole, Axelar, Chainlink CCIP)
 + Understanding of MEV strategies (Flashbots, sandwich attack defense, Searcher bot development)
 + Security background: Familiarity with DeFi attack vectors and defense strategies
 + Contributions to open-source projects
 + Prior experience in Web3, DeFi, or related ecosystems

## Description

We are seeking an experienced Senior Engineer to join our core development team to lead the design and implementation of our next-generation cross-chain lending protocol. This role focuses on smart contract security and architecture and the development of critical off-chain services that ensure the protocol's efficiency and robustness.
What You'll Do:

 + Design, develop, and optimize DeFi protocols on EVM-compatible chains, emphasizing contract architecture, security, gas optimization, and upgradability
 + Develop key backend and off-chain services in Go or Python, including monitoring systems, liquidation bots, and liquidity rebalancers
 + Tackle cross-chain integration challenges, ensuring atomicity, data consistency, and reliable asset bridging in an asynchronous environment
 + Rapidly iterate in an Agile environment and produce robust documentation and system architecture diagrams
Who You Are


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