Senior Engineer — Payments APIs & Tokenization

Kindredventures; United States; On-site; USD 140,000 - 190,000; Full time

Job summary

Basis Theory seeks a Senior Product Engineer to build tokenization, payments orchestration, and multi-tenant API infrastructure at scale. You will own critical platform components end-to-end, from API design through production operations, leveraging AI tooling to accelerate delivery.

You will collaborate with engineers and cross-functional teams to deliver reliable, high-quality APIs and systems that serve AI-native customers and traditional integrations.

Qualifications

• Backend API-based systems development experience.
• Strong problem-solving enabling full-stack contribution.
• Test automation with a high quality bar.
• Experience designing and/or publishing REST APIs.
• Proficiency developing APIs with C#, Java, or comparable language.
• Experience using AI coding assistants and LLM-based tools to accelerate engineering workflows.

Responsibilities

• Design, build, and ship features across the tokenization platform, payment orchestration layer, and multi-tenant API infrastructure.
• Drive technical design decisions for complex systems balancing performance, compliance, and customer needs with minimal guidance.
• Lead delivery of cross-cutting features from design through production rollout and resolve roadblocks.
• Own the reliability and evolution of platform components, shipping improvements.
• Build APIs consumed by developers and AI agents with clear, consistent interfaces.
• Leverage AI coding tools to accelerate development and improve code quality.
• Collaborate with engineers through pairing, reviews, and guidance to raise team standards.
• Partner with customers, sales, and support to address real-world usage.

Skills

Backend API development

Full-stack mindset

Test automation

REST API design

C# / Java proficiency

AI tooling familiarity

Tools

AWS

GitHub Actions

Azure DevOps

Job description

Senior Product Engineer:

As a Senior Product Engineer at Basis Theory, you will build the infrastructure that powers how businesses tokenize, store, and move sensitive data — at scale, under strict compliance, and with the reliability that payments demand. You'll own critical platform components end-to-end: from API design through production operations.

In this role, you'll leverage AI tooling and deep technical expertise to ship faster, make sound technical design decisions, and build systems that serve both traditional integrations and the next generation of AI-native customers.

What you'll be responsible for:

• Design, build, and ship product features across our tokenization platform, payment orchestration layer, and multi-tenant API infrastructure.
• Drive technical design decisions for complex systems — balancing performance, compliance constraints, and customer needs with minimal guidance.
• Lead delivery of cross-cutting features end-to-end: from technical design through production rollout, proactively resolving roadblocks.
• Own the reliability and evolution of platform components, continuously identifying risks and shipping improvements.
• Build APIs that are consumed by both developers and AI agents — designing for clarity, consistency, and machine-readability.
• Leverage AI coding tools to accelerate development workflows, improve code quality, and push the boundaries of what a small team can ship.
• Collaborate with other engineers through pairing, design reviews, and technical guidance — raising the bar across the team.
• Partner with customers, sales, and support to understand real-world usage and deliver solutions that solve actual problems.

You may be a good fit if:

• You're a builder first — you want to ship product, not just write code.
• You have deep backend expertise (C#, Java, or similar) and the aptitude to become proficient in our other core languages (Go, JavaScript, Swift).
• You care about the details: performance, API ergonomics, and the quality of the developer experience you're shipping.
• You have a high bar for code quality and test automation — you don't ship without confidence.
• You leverage tools like Claude, GPT, or similar to accelerate your engineering work and are curious about how AI changes what's possible in product development.
• You thrive in a collaborative, low-ceremony environment where engineers own outcomes, not just tasks.
• You have a proactive, problem-solving mindset — you find issues before they find customers.
• You're a lifelong learner who's energized by working at the intersection of payments, security, and developer tools.

Other experiences that may help:

• High-velocity transactional systems (hundreds of millions of API calls per week).
• Payment engineering in a PCI Level 1 environment.
• Building multi-tenant platforms where isolation and compliance are non-negotiable.
• Load testing and performance engineering at scale.
• Designing APIs consumed by LLM agents or AI-native applications.

Skillsets

Required

• Backend engineering experience building API-based systems
• Deep problem-solving skills that enable full-stack contribution
• Test automation experience with a high quality bar
• Experience designing and/or publishing REST APIs
• Proficiency developing APIs with C#, Java, or comparable language
• Experience using AI coding assistants and LLM-based tools to accelerate engineering workflows

Desired

• CI/CD or DevOps experience (GitHub Actions, Azure DevOps, etc.)
• Experience with AWS cloud services
• Experience with systems operating at high-velocity API throughput (>30m requests per week)
• Experience building features that integrate AI/LLM capabilities or serve AI-native use cases

Experience

• 5+ years of experience in software development, building and operating API-based systems. Bonus if that experience is in payments, fintech, or compliance-heavy environments.