Smart Contract Engineer

X-Team; United States; On-site; USD 180,000 - 280,000; Full time

Benefits offered by this job

Remote work

Overlap with US/EU hours

Job summary

X-Team is seeking a senior software engineer to design and implement secure, gas-optimized Solidity contracts powering next-generation DeFi protocols. You will write extensive tests, prepare for audits, and work with risk, frontend, indexer, and quantitative teams to ship robust, end-to-end dApps.

The role emphasizes on-chain security, upgradeable patterns, and collaboration across cross-functional teams to deliver resilient infrastructure.

Qualifications

• 4+ years of professional software engineering experience with 2+ years writing secure Solidity contracts.
• Expertise in gas optimization, security patterns, and upgradeable proxy designs.
• Deep understanding of DeFi primitives and on-chain risk mitigation.

Responsibilities

• Design and implement secure, gas-optimized Solidity contracts for lending, vaults, and related mechanisms.
• Develop extensive tests (unit, integration, fork, fuzz, invariants) to ensure resilience.
• Prepare codebases for external audits and remediate findings proactively.
• Collaborate with risk, frontend, indexer, and quantitative teams to ship end-to-end dApps.

Skills

Solidity

EVM internals

DeFi primitives

Security mindset

AI-assisted coding

Tools

Foundry (Forge/Cast)

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

• 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)