Backend Engineer, San Francisco

fun.xyz; San Francisco (CA); On-site; USD 150,000 - 300,000; Full time

Job summary

Fun.xyz is building the backend that powers Web3 payments infrastructure. This role designs, builds, and maintains high-performance APIs and services that handle asset movement, settlement, and routing across providers, with a focus on reliability and scalability in a global user base.

You’ll collaborate with product and protocol teams, write clean code, participate in reviews, and contribute to incident response.

Qualifications

• Production backend experience with modern languages.
• Proficiency in TypeScript.
• Strong knowledge of distributed systems, APIs, and database design.
• Hands-on experience with cloud platforms and containerization technologies.
• Solid CS fundamentals and problem-solving skills.
• Clear communicator who can collaborate with cross-functional teams.

Responsibilities

• Design, build, and maintain high-performance APIs and backend services.
• Build new features to advance product experience.
• Collaborate with product and protocol teams to meet business requirements.
• Write clean, well-tested code and participate in code reviews.
• Contribute to incident response and debugging production issues.

Skills

TypeScript

Distributed systems

APIs

Database design

Cloud platforms

Containerization

CS fundamentals

Problem solving

Cross-functional collaboration

Tools

Docker

Kubernetes

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.

About the Role

We’re looking for a BackEnd Engineer to join our growing team at Fun and help architect the backend services that power our web3 payments infrastructure. This role is foundational to the success of our platform and will shape how payments, settlement, and transaction routing are handled across chains and payment providers. You’ll be working on high-performance, low-latency systems that support complex use cases like asset conversion, identity and security verification, transaction finality, and decentralized routing—while ensuring fault tolerance, scalability, and compliance across a global user base.

Team: Payments Infrastructure – Mid, Senior, Staff, or Principal Levels

Responsibilities

• Design, build, and maintain high-performance APIs and backend services that power our Web3 payments platform
• Build new features to further our product experience
• Collaborate with product and protocol teams to architect technical solutions that meet business requirements
• Write clean, well-tested code and participate in code reviews to maintain high engineering standards
• Contribute to incident response and debugging production issues to ensure system reliability

Requirements

• Strong experience building production backend systems with modern languages
• Proficiency in Typescript
• Deep understanding of distributed systems, APIs, and database design principles
• Hands-on experience with cloud platforms and containerization technologies
• Solid grasp of computer science fundamentals including data structures and algorithms
• Strong problem-solving skills with ability to debug complex technical issues
• Clear communicator who can collaborate effectively with cross-functional teams

Nice to Have

• Production TypeScript experience
• Previously worked at crypto startup or Web3 infrastructure company
• Experience with blockchain integrations, smart contracts, or DeFi protocols
• Background with high-scale payment processing or financial compliance systems
• Contributions to open source projects or technical writing
• Experience with event-driven architectures and real-time data processing

$150,000 - $300,000 a year

Why Join Us

• Shape the future of payments and programmable money
• Work with bleeding-edge tech in a domain where innovation moves fast
• Join a mission-driven team focused on access, openness, and trust
• Be a key contributor, not just a cog—your work will ship fast and matter
• Collaborate with top-tier protocols, builders, and financial infrastructure providers

Location and Work Environment

This role is primarily in-person at our Midtown, NYC headquarters. We work together Monday through Thursday for fast, iterative collaboration and optional WFH Fridays to reset and recharge.