Protocol Engineer

About the Company

Fun.xyz builds crypto payment infrastructure that makes onchain value transfer intuitive, secure, and seamless for everyday users and developers. Its flagship product, Checkout, is a high-conversion payment solution that lets users complete any onchain action using assets from self‑custodial wallets, centralized exchanges, or on-ramped fiat from cards and bank accounts. By aggregating routing and exposing users' full asset portfolios at the point of sale, Checkout helps dApps drive faster, stickier, more engaged users without stitching together multiple providers or spinning up new chains.​
If you believe anyone, anywhere should be able to purchase anything with any asset, Fun.xyz is a place to build that future

About the Role

Fun.xyz is expanding its core blockchain team with a Protocol Engineer who can help define the foundation of its Web3 payments infrastructure. This is a high-impact role at the intersection of smart contracts, cross-chain protocols, and DeFi, focused on secure and efficient onchain systems that enable millions of transactions across multiple networks.​
You will be another version of Fun's existing Solidity engineer: deeply crypto-native, comfortable owning protocol design and implementation, and able to collaborate closely with backend and product teams.

Key Responsibilities

• Design, develop, and deploy secure smart contracts and protocol components across multiple blockchain platforms.​
• Architect blockchain solutions for payments and settlement in collaboration with backend and product teams, translating business requirements into robust onchain designs.​
• Write highly efficient, well-tested contract code and participate in internal and external security reviews.​
• Research and evaluate new chains, DeFi primitives, and interoperability protocols for potential integration into Checkout.​
• Support incident response and debugging of onchain issues to ensure protocol reliability.​

Requirements

Proven experience building and deploying production smart contracts on major blockchain platforms (e.g., Ethereum/L2s).​

Hands-on expertise with one or more smart contract languages: Solidity (preferred), plus Rust or Move a strong plus.​

Solid grasp of DeFi protocols, token standards, and cross-chain communication patterns.​

Strong security mindset, including awareness of common smart contract vulnerabilities and best practices.

Bonus Skills

• Deep understanding of blockchain architecture, consensus mechanisms, and applied cryptography concepts used in smart contract systems.​
• Production experience across multiple ecosystems (L1s and L2s), including non-EVM chains.​
• Familiarity with cross-chain bridges, oracles, and interoperability frameworks.​
• Experience with formal verification or advanced contract testing frameworks (e.g., Foundry, Echidna).​
• Contributions to open-source blockchain projects or protocol research