Senior Full-stack Engineer - Agentic Payments (NYC / MIA)

Crossmint•New York, NY

5h•$200,000 - $230,000•Hybrid

About The Position

As a Senior Full-stack Engineer on the Agentic Payments Team, you will build and scale the infrastructure that lets AI agents transact safely and autonomously including the agent wallets, delegated authorization, checkout, and card rails that enterprises and developers use to give their agents real spending power. Your work will directly impact how companies let agents hold funds, make purchases, and pay for services strictly within the guardrails their users define. You'll build our offering across stablecoin rails and the major card networks' agentic programs, including Visa Intelligent Commerce, Mastercard Agent Pay, and more. You will ship enterprise-grade, production-ready services that developers integrate in minutes through secure APIs and SDKs.

Requirements

Strong communication skills in written and spoken English.
Bachelor's degree in Computer Science or equivalent professional experience.
7+ years building production systems, with a strong backend and full-stack track record.
Strong programming skills in at least one modern language such as TypeScript (ideal), JavaScript, Java, Python, or similar.
Experience with payments, card issuing/processing, transaction systems, or wallet/agent infrastructure.
Solid understanding of payment flows — authorization, settlement, and tokenization — and/or blockchain fundamentals such as smart contract interactions, gas abstraction, and transaction lifecycles.
You are opinionated about how to make endpoints and interfaces usable and ergonomic for agents as first-class users, and how to engineer modern AI-first systems and workflows.
A product and ownership mindset with an ability to balance usability, security, and long-term reliability.
A track record of owning complex systems end to end and mentoring other engineers.

Nice To Haves

Familiarity with agentic payment protocols and standards (x402, AP2/A2A, ACP) and/or card-network agent programs (Visa Intelligent Commerce, Mastercard Agent Pay).
Experience with card issuing/processing, PCI-scoped systems, or payment orchestration at scale.
Familiarity with EVM ecosystems, Solana, Stellar, or multi-chain stablecoin payments.
Built and published skills, CLIs or MCP tools or have contributed to notable agentic harnesses or AI surfaces.
Prior experience at a crypto-native, Web3, fintech, or payments engineering team.

Responsibilities

Write high-quality production code that is correct, secure, performant, and maintainable.
Build and scale agent wallet infrastructure: provisioning, signing flows, transaction orchestration, and lifecycle management for wallets owned and operated by AI agents.
Design and enforce delegated authorization and programmable guardrails for spending limits, merchant allowlists, human-in-the-loop approval thresholds, and auditable transaction logs that let agents act autonomously within defined boundaries.
Integrate agentic card rails, including Visa Intelligent Commerce, Mastercard Agent Pay, and emerging agent payment programs covering virtual card issuance, tokenization, and lifecycle.
Build agent commerce and checkout experiences, from conversational checkout to programmatic purchasing, exposed through clean APIs and SDKs.
Design scalable, secure systems that bridge agents, card networks, and onchain/offchain components while maintaining data integrity and compliance.
Contribute to architecture and design documentation to shape the long-term evolution of Crossmint's agentic payments products.
Own features end to end from design to production deploy and iteration.
Participate in paid on-call rotations once or twice per quarter.
Mentor and support teammates and help raise the technical bar across the engineering organization.

Benefits

Extensive access to leading AI tools and subscriptions, with AI actively encouraged and integrated into daily workflows.
Two performance reviews annually.
Stock options are part of every full-time offer.
Unlimited, flexible PTO.
Parental Leave program.
Flexible work schedule.
Company laptop and allowance for any necessary home equipment.
Daily stipend for commuting to the office and/or meals.
Three company-paid off-sites per year.
Health, dental, vision, life, short-term disability (STD), and long-term disability (LTD) insurances.
401(k) Plan.