Senior Software Engineer, Backend (AI Platform)

Description

The company gives people a clear, predictable way to pay over time, with no hidden fees or surprises.

Engineering is building large-scale, fault-tolerant, global infrastructure shared by several financial products, merchants, and vendors. Keeping that infrastructure open to every engineer is central to the business. Engineers write blameless postmortems and detailed tech specs, and gather feedback before major system changes.

The AI Platform team builds the standard way to build, run, evaluate, and govern AI systems. Its users are every engineer and a growing number of production workloads. The team provides simple, governed access to models, tools, and agents, with identity, cost attribution, reliability, and security included.

Current components include an LLM gateway in front of every approved model (Claude, ChatGPT, and open-weight models on AWS Bedrock and other providers), an MCP gateway that mediates and audits tool calls, an agent runtime with bounded execution for agentic workloads, and an evals and observability layer that shows whether an AI change is better, cheaper, or safe to ship.

The platform is early. The gateway is used daily across engineering, the first production agent is live, and over the next year the work moves from developer productivity to production inference and agents.

Responsibilities

• Drive technical decisions and projects from initial design to launch, including on-call duty.
• Build the gateway, runtime, and evaluation services that carry AI workloads through pilot and into live use, keeping them secure as they scale to millions of users and their transactions.
• Make AI spending attributable and governable by building identity, quota, routing, caching, and failover controls, so teams can adopt new models and tools without rebuilding the same platform pieces.
• Work with security, infrastructure, and product engineering to define guardrails for agentic workloads and the on-behalf-of identity model for tool access.
• Define and track metrics for your team's systems, and own their operational health: monitoring, alerting, runbooks, and on-call.
• Set and raise code review and design standards, and promote them beyond your team through writing and tech talks.
• Mentor and develop engineers on the team, and build good practices for design, coding, and testing.
• Use AI tools and agentic workflows daily to speed up your coding, design reviews, and operations, and push the team on what a small AI-native team can ship.

Requirements

• 4+ years designing, developing, and launching backend systems at scale, using languages such as Python or Kotlin.
• A track record of building highly available distributed systems with technologies such as AWS, MySQL, and Kubernetes.
• Hands-on production experience with LLMs, agents, or AI frameworks: inference APIs, LLM gateways (LiteLLM or similar), MCP, tool calling, evals, or agent runtimes.
• An understanding of how AI is used and what infrastructure is needed to support AI workloads across disciplines.
• Experience writing a technical plan for a significant feature or component, with a design that is elegant, simple, and extensible. You write high-quality code that others can easily read and use.
• Skill at making large changes in a big codebase, with tools and practices that let you and your team do this safely.
• You take ownership of your growth and actively seek feedback from your team, your manager, and stakeholders.
• Strong verbal and written communication to collaborate with the global engineering team.
• Equivalent practical experience or a Bachelor's degree in a related field.

Conditions

Equity grade 9.

New hires usually start at the bottom of the pay range. Pay is set using a simple, transparent structure based on location, experience, and job-related skills.

Base pay is part of total compensation, which may also include equity, monthly stipends for health, wellness, and tech spending, and benefits.

USA base pay range in CA, WA, NY, NJ, and CT: $195,000 to $255,000 per year.

USA base pay range in all other U.S. states: $173,000 to $233,000 per year.

Remote position.

The company is remote-first. Most roles can be done from almost anywhere in the country of employment. Some may occasionally need in-person work at an office, and a few are office-based. All new hires attend an in-person onboarding.

The company offers an inclusive interview process with accommodations for candidates with disabilities. For San Francisco or Los Angeles roles, qualified applicants with arrest and conviction records are considered, as required by law.

Benefits

• Medical, dental, and vision coverage at no cost to you, with 100% of premiums covered for you and your dependents.
• Monthly stipends for tech setup and for health and wellness options that suit you.
• Flexible time off and a generous holiday calendar so you can rest when needed.
• An employee stock purchase plan (ESPP) that lets you buy company stock at a discount.