Senior Software Engineer - Payments

Order.co is the System of Action for the Office of the CFO, transforming the way businesses purchase and pay into an intuitive, B2C-like shopping experience. Order.co leverages embedded AI agents and embedded financial products to reinvent the way businesses connect with their vendors. 

End users enjoy a seamless, zero-training buying experience, while finance and procurement leaders gain a single platform to orchestrate how the business “should operate”. The result is an all-in-one solution that serves as a gravitational pull for spend and data, automating and eliminating procurement and finance workflows from requisition to reconciliation along the way.

Order.co is on the cutting edge of B2B Agentic Commerce, poised to be the market leader in creating a more predictive, prescriptive, and personalized experience for users. 

Founded in 2016 and headquartered in New York City, Order.co oversees nearly half a billion in annualized spend across hundreds of customers like WeWork, SoulCycle, Lume, and [solidcore]. Order.co has raised $75M in funding from industry-leading investors like MIT, Stage 2 Capital, Rally Ventures, 645 Ventures, and more. Order.co has been proudly named a 50 to Watch by Spend Matters and a Best Place to Work by BuiltIn and Inc. Magazine.

The Role

As a Senior Software Engineer on the Payments team, you will own the software that moves real money for Order.co's customers — virtual-card issuance and authorization, bank connections, accounting integrations, recurring and consolidated invoicing, and ACH / RTP rails. You'll deliver complex features reliably, own subsystems end-to-end from initial design through rollout and post-release fixes, and mentor junior and mid-level engineers along the way. You'll be a credible technical voice in design discussions, challenge weak assumptions early, and help the team build software that is correct, maintainable, and secure — qualities that matter especially in code paths where a bug shows up on a customer's bank statement. Along the way, you'll grow your architectural judgment in money-movement systems and predictably ship work that moves the business forward.

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. The team routes questions to you for these areas
• 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 where a quick patch can hide a deeper consistency bug

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. In payments, that includes double-charge, double-credit, dropped webhook, and out-of-order event scenarios

End-to-End Delivery & Ownership

• Scope and estimate work accurately; solve problems in order — break down epics into deliverable, independently reviewable units
• Deliver features end-to-end, including rollout coordination and post-release monitoring. Rollouts that affect real money rely on feature-flagging, dark-launching, reconciling, and watching dashboards before declaring "done"
• Communicate risks and blockers early — don't absorb uncertainty silently
• 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 to help, and catch what AI misses; teach others to do the same
• 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

Qualifications

• You are motivated by accountability — you own outcomes, not just tasks
• You are results-oriented and measure success by shipped, working software
• You are motivated by correctness in code that touches money — the consequences of a bug land on real customer balances, and you take that seriously
• You love helping people on your team grow and improve
• Writing tests is an integral part of your development process, not an afterthought
• You know how to design and build software incrementally — you don't need a complete spec to make progress
• Collaborating with the people around you to achieve a goal motivates you
• You are collaborative, open-minded, and actively developing your craft
• You are curious and pragmatic about AI-driven solutions — you apply them where they add real value and stay skeptical where they don't
• Familiarity with AI-assisted development tools — you understand how they work, where they help, and where they fail. Prior hands-on use is a plus; intellectual curiosity and the instinct to evaluate AI output critically are what matter

Technical Skills

• 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
• Experience using AI coding assistants (e.g., Claude, GitHub Copilot) as part of your development workflow — not as a shortcut, but as a force multiplier; you provide them with appropriate context about constraints and conventions, critique AI output, recognize failure modes, and decide when to override

What Great Looks Like

A Senior Software Engineer on the Payments team who is thriving at this level demonstrates:

• Reliable delivery of complex work — consistently ships multi-part features on time with low defect rates
• Low defects in owned areas — proactively monitors and improves the quality of the systems they own; in payments specifically, that means incident-free quarters in code paths that move funds and clean reconciliation against vendor reports
• High trust from team and stakeholders — engineers, Finance, Operations, and Credit partners know they can count on you
• Measurable mentorship impact — engineers around you write better code because of your reviews and guidance

"Someone we can depend on for the work that matters — especially the work that touches money."

Failure Modes We Screen Against

We actively evaluate candidates for the following anti-patterns during the interview process:

Interview Process

Our 5-round process is designed to evaluate you across all competency areas. AI tools are permitted in technical rounds.

Round 4 is conditional: it runs when the team needs additional behavioral signal after Rounds 2 and 3, and is otherwise skipped. Your recruiter will tell you whether it's scheduled before your loop is finalized.

The Round 2 (Take-Home + PR Discussion) and Round 3 (System Design) exercises are drawn from real payments problems — invoice payment allocation and credit-availability calculation — so the technical evaluation is grounded in the work you'd actually be doing.

What You’ll Receive

• Competitive compensation
• Employer-sponsored 401(k) with match
• Comprehensive medical, dental, and vision coverage
• Flexible time off and hybrid work environment
• Opportunity to build and scale a critical function at a high-growth fintech company

The anticipated annual salary range for this role is $175,000–$195,000. Actual compensation and title will be commensurate with experience, qualifications, knowledge, and skills.