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Software Engineer, Payments Infrastructure

Sierra· Engineering
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San Francisco, CA$230k - $390kFull-timePosted 4mo ago

About the role

Software Engineer role focused on building and operating the payments infrastructure for a real-time, card-data–driven platform. Responsibilities span payments, security, real-time voice, and LLM integration, with emphasis on preserving PCI DSS compliance, tokenization, egress controls, and secure, self-serve payments across agent tooling.

Responsibilities

  • Build real-time card capture for voice: intercept keypad and spoken digits in a live audio stream, upstream of the agent runtime in a network-segmented environment, while the LLM stays live on the call.
  • Build and extend the tokenization platform: agents receive and send short-lived tokens, and the platform swaps a token for the real value only when it calls the customer's payment gateway.
  • Own the payments egress control plane: every destination for card data is approved, versioned with the agent release, and enforced by infrastructure below the application, not by convention.
  • Make payment actions correct: an at-most-once action primitive in the Agent SDK, validated amounts and items, and monitoring that compares what the agent said about a payment with what really happened.
  • Keep card data out of places it should not be: deterministic detection in the agent's hot path that catches what general-purpose models miss. No LLM, including any we build ourselves, ever sees a plaintext card number.
  • Make payments self-serve: one payments API across Agent Studio, the Agent SDK, and Ghostwriter; gateway middleware that developers write against tokens; and support for single-tenant and customer-cloud deployments.
  • Grow the platform beyond cards: extend tokenization into a privacy vault for all PII.

Qualifications

  • 5+ years building backend, platform, or infrastructure systems, with a track record of shipping and operating high-reliability services in production.
  • A deep security instinct and design approach focused on blast radius, least privilege, and fail-safe states.
  • Rigor about correctness under failure: retries, idempotency, at-most-once behavior, and robust timeout handling.
  • Fluency in a systems language (Go) and comfortable owning critical systems end to end.
  • Range and ownership mindset with ability to build abstractions over external systems and work across teams.
  • Clear communication to both engineers and non-engineers about design and risks.
  • Degree in Computer Science or related field, or equivalent professional experience.

Skills

Required:Backend / infrastructure developmentSecurity best practicesGo (Golang)

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, snacks and coffee
  • Discretionary benefit stipend
  • Free alphorn lessons
Last updated Oct 7, 2026. Interested? Apply on the company site.
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About Sierra

Better customer experiences. Built on Sierra.

Sierra helps businesses build better, more human customer experiences with AI.

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