Software Engineer, Payments Infrastructure

Sierra • San Francisco, CA

4d • $230,000 - $390,000 • Onsite

About The Position

The Payments Infrastructure team builds the trust boundary between a live conversation and the rest of Sierra: sensitive data enters through a customer's voice or chat, leaves as a token, and the agent never sees the plaintext in between. Doing this well means weaving four hard domains together at once: LLMs, payments, infrastructure, and voice. Done right, it unlocks seamless, compliant payments for every Sierra agent and the people who use them. It's already one of the highest-containment features Sierra ships: when an agent can take a payment, the conversation keeps going instead of transferring to a person, so the agent resolves everything around it too. The platform is PCI DSS Level 1, on Visa's Global Registry, and carries cardholder data across millions of payment lifecycle events for enterprise customers.

Requirements

• 7+ years building backend, platform, or infrastructure systems, with a track record of shipping and operating high-reliability services in production at a strong engineering organization.
• A deep security instinct. You design as though every component will eventually be compromised, and you reason naturally about blast radius, least privilege, and making bad states impossible rather than reacting to them.
• Fluency in a systems language (we use Go) and comfort owning critical distributed systems end to end, from design through production and on-call.
• A record of setting technical direction on ambiguous, high-stakes problems, and getting the abstractions right so they hold up across teams and customers.
• A generalist's instinct. You build clean abstractions and protocols over messy, inconsistent external systems, and you're never satisfied solving a problem once per customer.
• Degree in Computer Science or a related field, or equivalent professional experience.

Nice To Haves

• Experience in a regulated or sensitive-data domain such as payments, PCI, tokenization, key management, or healthcare and PHI.
• Depth in one of our core areas: applied cryptography and key management; voice, telephony, or real-time media pipelines; or cloud security and network isolation.
• Experience building platforms other engineering teams build on, such as internal protocols, SDKs, and self-serve developer services.

Responsibilities

• Design the secure-capture protocol every channel sits behind, so the payment feels like one continuous conversation to the person on the other end, while telephony providers, contact-center platforms, embedded chat, and Sierra's own voice stack all present a single event lifecycle to agent code, no matter how different each customer's stack is.
• Build and extend the tokenization platform: per-token envelope encryption with a unique data key per token, so a single compromised decrypt exposes one token at most.
• Own the security perimeter around the cardholder-data environment, so what each system can reach is enforced by infrastructure rather than convention, and auditable by design.
• Build deterministic, auditable detection in the agent's hot path that catches the cardholder data general-purpose models miss, and help design the purpose-built detection model that comes next. No LLM, including any we build ourselves, ever sees plaintext cardholder data.
• Make payments something other engineers can use without becoming compliance experts: drive the platform toward processor-agnostic charging, self-serve onboarding, and single-tenant deployments, so a team can add payments to an agent without a payments infrastructure engineer in the loop.
• Set technical direction across the team's hardest problems, get the abstractions right so we solve each one once rather than per customer, and raise the bar for the engineers around you.

Benefits

• Flexible (unlimited) paid time off
• Medical, dental, and vision benefits for you and your family
• Life insurance and disability benefits
• Retirement plan dependent on country of employment
• Parental leave
• Fertility and family building benefits through Carrot
• Lunch, as well as delicious snacks and coffee to keep you energized
• Discretionary benefit stipend giving people the ability to spend where it matters most
• Free alphorn lessons

What This Job Offers

• Job Type: Full-time
• Career Level: Senior