Senior BlockChain Engineer — Contract (Remote, Germany)

Contract length: 12 months

Work mode: Remote — some overlap with US working hours required (client is US-based)

Location:Germany

About the role

We are seeking a Senior Solidity Engineer to join a fast-moving blockchain team focused on building secure, robust smart-contract systems for financial products. You will design, implement, test and maintain Solidity smart contracts, drive security best practices, and collaborate across frontend, backend and product teams to deliver production-grade decentralized systems.

Key responsibilities

• Design, develop, test and deploy Solidity smart contracts and related on-chain infrastructure.
• Write and maintain unit, integration, fork and invariant tests to ensure long-term code quality.
• Use Hardhat and/or Foundry for development, testing and deployments.
• Perform and act on security reviews, threat models and on-chain vulnerability findings.
• Integrate smart contracts with web3 frontends and backend services; collaborate closely with product managers and engineers.
• Maintain and enhance existing contracts, handle live-contract incidents and issue remediation.
• Keep up to date with cryptography, blockchain protocol changes and DeFi innovations; propose and implement improvements.
• Communicate technical concepts clearly to both technical and non-technical stakeholders.

Must-have skills & experience

• Demonstrable hands-on experience developing Solidity smart contracts.
• Strong understanding of blockchain security practices and common smart-contract vulnerabilities (reentrancy, integer over/underflows, access control, front-running, oracle manipulation, etc.).
• Proficiency with Hardhat and Foundry.
• Experience with Solidity security/static/fuzz testing tools such as Slither, Mythril and Echidna.
• Practical scripting experience in JavaScript or TypeScript.
• Strong experience writing unit, integration, fork and invariant tests.
• Solid CS fundamentals — data structures, algorithms, and software engineering best practices.
• Excellent debugging and troubleshooting skills.
• Strong written and verbal communication in English; ability to explain technical issues to non-technical stakeholders.
• Bachelor’s degree in Computer Science, Engineering, or related STEM discipline.
• Development experience in banking/finance/trading or deep understanding of financial instruments and systems.

Bonus / nice-to-have

• Experience with financial infrastructure: collateral management, lending, balance-sheet systems.
• Familiarity with Chainlink tools (CCIP, Data Feeds, VRF, Automation).
• Multi-chain / cross-chain smart contract development experience.
• Prior work with DeFi protocols (Aave, Uniswap, MakerDAO, etc.).
• Experience with ZK (zero-knowledge) technologies.
• Advanced STEM degree or blockchain/smart-contract certifications.

Candidate profile

• Senior, self-motivated engineer who thrives in a fast-paced environment.
• Security-first mindset with a track record of shipping reliable on-chain systems.