Smart Contract Engineer

X-Team; United States; Remote; USD 180,000 - 240,000; Full time

Job summary

X-Team is seeking a senior protocol engineer to design, implement, and deploy secure on-chain infrastructure. You will own smart contract architecture from modeling to mainnet deployment, audits, and live monitoring.

This full-time, fully remote role requires hands-on experience with DeFi primitives, rigorous testing, and threat modeling to ensure upgradeable, cost-efficient, and resilient code in production.

Qualifications

• 4+ years of professional software engineering with at least 2+ years in production Solidity contracts.
• Expert-level Foundry (Forge, Cast) mastery including fuzzing and mainnet fork simulations.
• Deep understanding of EVM internals, gas optimization, Yul, and proxy/upgrade patterns.
• Practical knowledge of DeFi primitives (ERC-20/4626/721/1155, AMMs, oracles, liquidations).
• Comfort using AI coding tools to speed testing and documentation with sound judgment.
• Security-minded with awareness of reentrancy, oracles, front-running, etc.

Responsibilities

• Protocol Architecture: design and implement secure, gas-optimized Solidity contracts for lending, vaults, yield routing, liquidations, and access control.
• Testing & Simulation: write unit, integration, fork, fuzz, and invariant tests for zero-day resiliency.
• Security & Audits: prepare code for external audits and remediate findings.
• Cross-Functional Integration: collaborate with risk, frontend, indexer, and quantitative teams to build end-to-end dApps.

Skills

Solidity development

Smart contract security

EVM internals

DeFi primitives knowledge

Audits familiarity

Adversarial thinking

Tools

Foundry (Forge/Cast)

Mainnet fork simulations

Job description

This role is a full-time engagement with the client, fully remote. Open to LATAM, USA & Canada.

The Mission

Help build and scale the secure on-chain infrastructure powering the next generation of open finance. In this role, you’ll design, implement, and battle-test critical smart contracts that manage significant TVL and capital-efficient primitives. This isn't about deploying speculative tokens; it’s about constructing highly resilient, mathematical, and adversarial-resistant software that remains upgradeable, cost-efficient, and bulletproof over time.

The Role

As a core protocol contributor, you will take deep ownership of smart contract architecture from initial mathematical modeling and design through to mainnet deployment, external audit facilitation, and live monitoring.

• Protocol Architecture (40%): Design and implement secure, gas-optimized Solidity smart contracts for lending, borrowing, vaults, yield routing, liquidations, and access control.
• Testing & Simulation (30%): Write extensive unit, integration, fork, fuzz, and invariant tests utilizing modern frameworks to ensure zero-day resiliency.
• Security & Audits (15%): Prepare codebases for top-tier external audits, remediate findings, and design proactive on-chain risk mitigation/monitoring strategies.
• Cross-Functional Integration (15%): Collaborate closely with risk, frontend, indexer, and quantitative engineering teams to build seamless, secure end-to-end dApps.

The Must-Haves

• Experience: 4+ years of professional software engineering experience, with at least 2+ years writing, deploying, and maintaining highly secure Solidity smart contracts in production..
• Tooling & Frameworks: Expert-level mastery of Foundry (Forge, Cast) including advanced fuzzing, invariant testing, and mainnet fork simulations.
• EVM Deep Dive: Thorough understanding of EVM internals, storage layouts, gas optimization strategies, assembly (Yul), and standard proxy/upgradeability patterns.
• DeFi Primitives: Practical, working knowledge of core financial primitives (such as ERC-20/4626/721/1155, AMMs, lending pools, oracles, and liquidation engines).
• AI-Assisted Acceleration: Comfort using modern AI coding tools (e.g., Cursor, Claude, Copilot) to accelerate unit testing, documentation, and boilerplate development, backed by the critical judgment required never to trust raw model outputs blindly.
• Security Mindset: An obsessive awareness of common attack vectors (reentrancy, oracle manipulation, front-running, rounding errors, and access-control flaws).

The Bonus Skills

• Audit Pedigree: Prior experience guiding a protocol through a major external audit (e.g., Trail of Bits, OpenZeppelin, Spearbit) or participating in competitive security audits.
• Multi-Chain/SVM: Exposure to Rust-based smart contract environments (SVM/Solana, CosmWasm) or zero-knowledge (ZK) rollup architectures.
• Advanced Automation: Familiarity with off-chain automation infrastructure like Keepers, Defender, or Gelato.
• Adversarial Thinker: You don't just think about how code should work; you instinctively try to find ways to break, front-run, or exploit the state machine you are building..
• Execution & Ownership: You act as an owner, not a ticket executor. You proactively trace edge cases, optimize gas, and address technical debt before it is flagged..
• Detail-Obsessed: You care about the nuance of a single uint256 math operation and understand why rounding down vs. up is a security-critical decision..
• Collaborative & Clear: You can distill complex cryptographic or financial system logic into clear documentation and explain architectural tradeoffs to non-smart contract engineers..

Location: Remote (with meaningful overlap with US/EU working hours)