Senior Software Engineer, Backend (AI Platform)

Affirm, Inc.; United States; Remote; USD 173,000 - 255,000; Full time

Benefits offered by this job

Health coverage

Tech stipends

Flexible time off

ESPP program

Job summary

Affirm is seeking a Senior Software Engineer, Backend for the AI Platform, focused on building scalable, secure gateway and runtimes for AI workloads. This remote US role works with a world-class team shipping production-grade AI infrastructure used by thousands of users.

You will own design decisions, mentor engineers, and collaborate with security and product teams to ensure reliable and observable systems, while advancing the state of AI-enabled financial services.

Qualifications

• 4+ years of experience designing, developing and launching backend systems at scale.
• Proficiency with Python or Kotlin.
• Experience with AWS, MySQL, and Kubernetes in production.
• Hands-on experience with AI frameworks, inference APIs, or tool integration.
• Strong ownership, communication, and collaboration across teams.
• Bachelor's degree or equivalent practical experience.

Responsibilities

• Plan, execute, and own technical decisions for AI Platform backend.
• Design and build gateway, runtime, and evaluation services for AI workloads at scale.
• Implement identity, quota, routing, caching, and failover controls for model usage.
• Collaborate with security, infra, and product teams to set guardrails for workloads.
• Create and monitor metrics; own reliability, runbooks, and on-call processes.
• Define code review standards and promote them across teams.
• Leverage AI tools to improve developer productivity and delivery.
• Mentor engineers and drive best practices in design, coding, testing.

Skills

Backend systems design

Distributed systems

Python or Kotlin

AWS

MySQL

Kubernetes

AI tooling

Education

Bachelor's degree or equivalent practical experience

Tools

AWS

MySQL

Kubernetes

LiteLLM or similar

Job description

Senior Software Engineer, Backend (AI Platform)

Remote US

At affirm, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most.

Affirm's engineering team is building a large-scale, fault-tolerant, and global infrastructure that is shared across multiple financial products, merchants, and vendors. Ensuring that our infrastructure is transparently available to all engineers is critical to the success of the business. We pride ourselves on our culture across engineering of writing blameless postmortems as well as writing detailed tech specs and gathering feedback before large changes to systems.

The AI Platform team owns Amplify's paved path for building, running, evaluating, and governing AI systems. Our customers are not only affirm users, but also every engineer and a growing set of production workloads at affirm. As a team, we are responsible for building and exposing simple, governed interfaces to models, tools, and agents, with identity, cost attribution, reliability, and security built in. Examples of components we own include the LLM Gateway that fronts every approved model (Claude, ChatGPT, and open-weight models across AWS Bedrock and other providers), the MCP Gateway that mediates and audits tool calls, the Agent Runtime that gives agentic workloads bounded execution, and the evals and observability layer that tells teams whether an AI change is better, cheaper, or safe to ship. We are early: the gateway is in daily use across engineering, the first production agent is live, and the next year takes us from developer productivity to production inference and agents.

What You'll Do

• Plan, execute, and own technical decisions and projects within the AI Platform team, from design through launch and on-call.
• Design and build the gateway, runtime, and evaluation services that take AI workloads at affirm from pilot to production, securely scaling across millions of users and their transactions.
• Make AI spend attributable and governable: build the identity, quota, routing, caching, and failover controls that let teams adopt new models and tools without re-solving the same platform problems.
• Partner with security, infrastructure, and product engineering teams to set the guardrails for agentic workloads and the on-behalf-of identity model for tool access.
• Create and monitor metrics for your team's systems, and own the operational health of what you ship: monitoring, alerting, runbooks, and on-call.
• Set and improve code review and design standards, and advocate for them beyond your team through writing and tech talks.
• Use AI tools and agentic workflows every day as a multiplier for your own code, design review, and operations, and push the team on what a small AI-native team can deliver.
• Educate, mentor, and grow engineers in the team, and drive best practices around design, coding, and testing.

What We Look For

• You have 4+ years of experience designing, developing and launching backend systems at scale using languages like Python or Kotlin.
• You have a track record of developing highly available distributed systems using technologies like AWS, MySQL and Kubernetes.
• You have practical experience building with LLMs, agents, or AI frameworks in production: inference APIs, LLM gateways (LiteLLM or similar), MCP, tool calling, evals, or agent runtimes.
• You understand AI usage and the infrastructure needed to support and leverage AI workloads across different disciplines.
• You have experience defining a technical plan for the delivery of a significant feature or system component with an elegant, simple and extensible design. You write high quality code that is easily understood and used by others.
• You are proficient at making significant changes in a large code base, and have developed a suite of tools and practices that enable you and your team to do so safely.
• Your experience demonstrates that you take ownership of your growth, proactively seeking feedback from your team, your manager, and your stakeholders.
• You have strong verbal and written communication skills that support effective collaboration with our global engineering team.
• This position requires either equivalent practical experience or a Bachelor’s degree in a related field.

Pay Grade - N
Equity Grade - 9

Employees new to affirm typically come in at the start of the pay range.Affirm focuses on providing a simple and transparent pay structure which is based on a variety of factors, including location, experience and job-related skills.

Base pay is part of a total compensation package that may include equity rewards, monthly stipends for health, wellness and tech spending, and benefits (including 100% subsidized medical coverage, dental and vision for you and your dependents.)

USA base pay range (CA, WA, NY, NJ, CT) per year: $ 195,000 - 255,000

USA base pay range (all other U.S. states) per year: $173,000-233,000

#LI-Remote

Remote-first with flexibility built in

Affirm is proud to be a remote-first company. Most roles can be done from almost anywhere within the country of employment. Some positions may occasionally require in-person work at an affirm office, and a few are office-based due to the nature of the work. All new hires will be invited to attend an in-person onboarding experience.

Benefits designed for you

Our benefits reflect our commitment to care, transparency, and flexibility. Here are a few highlights:

• Health coverage at no cost: We cover 100% of premiums for employees and their dependents.
• Spending stipends: Monthly stipends support your tech setup, and the ability to choose health and wellness options that are right for you.
• Time off to recharge: Flexible time off and generous holiday calendars help you rest when you need to.
• Own a piece of what you build: Our employee stock purchase plan (ESPP) lets you buy affirm stock at a discount.

We’re committed to providing an inclusive interview process, including accommodations for candidates with disabilities. If you need support, we’re happy to help.

For positions based in San Francisco or Los Angeles: affirm considers qualified applicants with arrest and conviction records, as required by law.

Demographic Survey Statement (US-based roles)

affirm is dedicated to building an inclusive culture where affirmers belong and have an equal opportunity to thrive.

To help us assess our outreach efforts, we invite candidates to voluntarily share information through a short demographic survey. This information is:

• Completely optional
• Anonymized and stored in aggregate
• Not accessible to recruiters or hiring managers at the individual level
• Never used in any hiring decision

Your decision to provide or withhold this information will not impact your candidacy in any way.

Voluntary Self-Identification

For government reporting purposes, we ask candidates to respond to the below self-identification survey. Completion of the form is entirely voluntary. Whatever your decision, it will not be considered in the hiringprocess or thereafter. Any information that you do provide will be recorded and maintained in aconfidential file.

As set forth in affirm’s Equal Employment Opportunity policy,we do not discriminate on the basis of any protected group status under any applicable law.

If you believe you belong to any of the categories of protected veterans listed below, please indicate by making the appropriate selection. As a government contractor subject to the Vietnam Era Veterans Readjustment Assistance Act (VEVRAA), we request this information in order to measurethe effectiveness of the outreach and positive recruitment efforts we undertake pursuant to VEVRAA. Classification of protected categoriesis as follows:

A "disabled veteran" is one of the following: a veteran of the U.S. military, ground, naval or air service who is entitled to compensation (or who but for the receipt of military retired pay would be entitled to compensation) under laws administered by the Secretary of Veterans Affairs; or a person who was discharged or released from active duty because of a service-connected disability.

A "recently separated veteran" means any veteran during the three-year period beginning on the date of such veteran's discharge or release from active duty in the U.S. military, ground, naval, or air service.

An "active duty wartime or campaign badge veteran" means a veteran who served on active duty in the U.S. military, ground, naval or air service during a war, or in a campaign or expedition for which an campaign badge has been authorized under the laws administered by the Department of Defense.

An "Armed forces service medal veteran" means a veteran who, while serving on active duty in the U.S. military, ground, naval or air service, participated in a United States military operation for which an Armed Forces service medal was awarded pursuant to Executive Order 12985.