Senior Software Engineer, Payments

Responsibilities

Technical Execution & Code Ownership

• Independently design and implement complex, multi-part features from requirements to production
• Own subsystems, services, or critical components in the payments stack — for example, the internal financial ledger, the virtual-cards issuance and authorization lifecycle, bank connections, or the invoicing and auto-debit pipeline
• Write clean, maintainable, production-ready code with consistent test coverage — money-movement code paths are held to a high test bar
• Navigate existing codebases with architectural discernment — identify sound patterns to build upon, recognize technical debt, and use AI tooling as an accelerant while applying your own judgment on correctness, security, and alignment with the system's direction
• Debug production issues effectively; seek first to understand — investigate evidence and identify root causes rather than applying band-aids, especially in webhook, retry, and reconciliation paths

Design & Architecture Contribution

• Participate actively in design reviews; your designs regularly influence team-level architecture decisions
• Propose sound technical designs that account for scalability, performance, and reliability trade-offs — and for payments-specific concerns like idempotency, exactly-once semantics, reconciliation between internal state and vendor reports, and clean separation between authorization and capture
• Identify risks before they become incidents — surface edge cases, data consistency concerns, and failure modes during planning (double-charge, double-credit, dropped webhook, out-of-order event scenarios)

End-to-End Delivery & Ownership

• Scope and estimate work accurately; break down epics into deliverable, independently reviewable units
• Deliver features end-to-end, including rollout coordination and post-release monitoring using feature-flagging, dark-launching, reconciling, and dashboards
• Communicate risks and blockers early
• Review stories critically before committing: ensure they're appropriately broken down and that dependencies are well understood by the team

Mentorship & Technical Leadership

• Mentor junior and mid-level engineers through code reviews, pairing, and direct feedback
• Provide high-quality, substantive code reviews — lead with humility, treat the author as a teammate, and catch what AI misses
• Teach best practices; your presence raises the quality of code around you

Technical Influence

• Influence technical decisions through credibility, not just seniority
• Drive improvements in team practices — testing patterns, observability for money-movement flows, code organization, and the bar for test coverage in code paths that move real funds
• Champion quality and standards; push back on shortcuts that create long-term cost — especially in code that touches funds or credit

Communication & Collaboration

• Explain technical decisions clearly to both technical and non-technical stakeholders
• Represent engineering well in product and cross-functional discussions, including with Finance, Operations, and Credit on reconciliation, credit-risk, and dispute-handling questions
• Translate vendor documentation (Stripe, Lithic, and others) into clear, scoped engineering work
• Approach all assignments with a security lens — actively look for vulnerabilities in your own code and in the code you review, with extra care in PII and PCI-adjacent paths

Requirements

• Strong foundation in computer science fundamentals: data structures, algorithms, and system design
• Expertise in building production-grade applications and services using Ruby and Ruby on Rails
• Extensive experience with PostgreSQL and SQL-based data modeling, including query optimization and performance tuning
• Deep understanding of web application security, observability, and scalable system architecture
• Proven ability to design, build, and maintain secure, scalable, and well-documented APIs
• Experience building integrations with external systems — REST/GraphQL APIs, webhooks, event-driven pipelines, or third-party vendor connections
• Hands-on experience with at least one payment processor or card issuer (Stripe, Lithic, Adyen, Marqeta, Braintree, or equivalents), or comparable fintech vendor work
• Working familiarity with at least one of: double-entry ledger design, idempotency / exactly-once patterns for webhooks and money-movement, ACH / wire / card-network basics, or reconciliation against vendor reports
• Familiarity with AWS and other cloud platforms, including infrastructure as code and CI/CD pipelines
• You are motivated by accountability — you own outcomes, not just tasks
• You are results-oriented and measure success by shipped, working software
• Writing tests is an integral part of your development process, not an afterthought
• You know how to design and build software incrementally
• You are collaborative, open-minded, and actively developing your craft
• Familiarity with AI-assisted development tools — you understand how they work, where they help, and where they fail

Nice-to-Haves

• Prior hands-on use of AI-assisted development tools