Protocol Engineer, San Francisco

Fun; San Francisco (CA); On-site; USD 180,000 - 260,000; Full time

Job summary

Fun is building the infrastructure powering Web3 payments and decentralized finance. We are seeking a Protocol Engineer to join our core blockchain team and shape secure, scalable on-chain primitives and cross-chain integrations.

You will design and implement production-grade smart contracts, collaborate with backend and product engineers, and participate in security reviews and audits to ensure protocol safety. The role offers fast-paced impact in fintech infrastructure.

Qualifications

• Production smart contracts on major blockchain platforms.
• Strong understanding of DeFi primitives and token standards.
• Ability to explain complex blockchain concepts to non-technical stakeholders.

Responsibilities

• Design, implement, and deploy secure smart contracts and protocol components.
• Collaborate with backend and product teams to meet requirements.
• Participate in security audits and formal verification efforts.
• Research new blockchain technologies and integration opportunities.
• Troubleshoot and debug on-chain issues to ensure protocol reliability.

Skills

Blockchain protocol knowledge

Security auditing mindset

Cross-chain concepts

Communication with cross-functional团队

Tools

Solidity

Rust

Move

Job description

Capital markets are undergoing a fundamental shift. Assets that live in fragmented systems and manual workflows are moving onto blockchains - systems designed to move and store value more transparently and efficiently.

While this unlocks more open and programmable financial systems, it also introduces significant complexity. For most users, interacting with this new infrastructure is still too difficult.

Fun builds the infrastructure that powers consumer-facing fintech applications - handling onboarding, account access, and money movement so users can interact with blockchain-based systems as seamlessly as they do with traditional finance.

For fintech builders, Fun provides a best-in-class onboarding and deposit stack that drives conversion and unlocks user growth. We operate at the intersection of financial infrastructure, complex engineering, and product experience.

Role Overview

We are looking for a Protocol Engineer to join our core blockchain team and help build the foundation of Web3 payments infrastructure. This high-impact role offers the opportunity to work on challenging technical problems at the intersection of smart contracts, cross-chain protocols, and decentralized finance.

You will design and implement secure, efficient smart contract systems and blockchain integrations that power millions of transactions across multiple chains. This role is perfect for a technically strong engineer who thrives in fast-paced environments and wants to shape the future of decentralized finance.

Responsibilities

• Design, develop, and deploy secure smart contracts and protocol implementations across multiple blockchain platforms
• Collaborate with backend and product teams to architect blockchain solutions that meet business requirements
• Write highly efficient, well-tested code and participate in security audits to ensure protocol safety
• Research and evaluate new blockchain technologies, protocols, and DeFi primitives for integration opportunities
• Contribute to incident response and debugging on-chain issues to ensure protocol reliability

Requirements

• Strong experience building and deploying production smart contracts on major blockchain platforms
• Deep understanding of blockchain architecture, consensus mechanisms, and cryptographic principles
• Hands-on experience with smart contract development languages (Solidity, Rust, Move, etc.)
• Solid grasp of DeFi protocols, token standards, and cross-chain communication patterns
• Strong security mindset with knowledge of common smart contract vulnerabilities and best practices
• Clear communicator who can explain complex blockchain concepts to cross-functional teams

Nice to Have

• Production experience with multiple blockchain ecosystems (Ethereum, Solana, L2s, etc.)
• Previously worked at crypto startup or Web3 infrastructure company
• Experience with cross-chain bridges, oracles, or interoperability protocols
• Background with high-volume DeFi protocols or DEX infrastructure
• Contributions to blockchain open source projects or protocol research
• Experience with formal verification or advanced smart contract testing frameworks

We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses and identifying potential inconsistencies or verification signals in application materials based on available information. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans. If you would like more information about how your data is processed, please contact us.