Senior Software Engineer, Back-end (Fraud)

Affirm; Spain (TX); Hybrid; USD 81,000 - 138,000; Full time

Benefits offered by this job

Visa sponsorship for Spain

Health and wellness benefits

Job summary

Affirm is a remote-first fintech company building fraud decisioning systems to protect buyers and merchants. We are seeking a Senior Software Engineer to design real-time fraud decisioning services in Python or Kotlin, extend the system to new markets, and collaborate with teams across North America.

You will build the platform for market-by-market launches, integrate region-specific vendors, and support AI-powered signals while maintaining high reliability.

Qualifications

• 5+ years of experience building backend systems at scale using Python or Kotlin.
• Experience with distributed systems and infrastructure using AWS, MySQL/PostgreSQL, and Kubernetes.
• Strong system design skills and a track record of delivering maintainable, extensible services.
• Fluency with AI-driven engineering - directing and reviewing AI-generated code and ensuring correctness, quality, and security.
• Proficiency in SQL and working with data-rich environments.
• Familiarity with CI/CD practices and safe production deployments.
• Strong written and verbal communication skills in distributed teams.
• Proactive, ownership-driven mindset with a focus on learning and team success.
• Nice-to-have: experience with Snowflake, dbt, Airflow, Chronosphere; internationalization or localization; fintech risk or real-time decisioning.

Responsibilities

• Own and deliver quarterly goals for your team and mentor engineers.
• Design and implement real-time fraud decisioning services and APIs in Python or Kotlin.
• Extend the Fraud Decisioning System to markets beyond the US.
• Build a scalable platform to launch fraud decisioning in new countries quickly.
• Integrate region-specific risk vendors and operationalize AI signals for real-time decisioning.
• Collaborate with Product, ML, Analytics, and Fraud Strategy across the lifecycle.
• Maintain systems with metrics, on-call readiness, and incident response.
• Foster quality and ownership through code reviews and mentorship.
• Participate in on-call rotation.

Skills

Python

Kotlin

Distributed systems

SQL

Tools

AWS

MySQL

PostgreSQL

Kubernetes

Snowflake

dbt

Airflow

Chronosphere

Job description

Senior Software Engineer, Back-end (Fraud)

Remote Spain

Affirm is reinventing credit to make it more honest and friendly, giving consumers the flexibility to buy now and pay later without any hidden fees or compounding interest.

The Fraud Engineering organization builds the foundational and tactical software that enables affirm to respond strategically to fraud - both in real time and after the transaction. Our mission is to support business growth while protecting affirm, our buyers, and our merchants. We evaluate risk at critical decision points in the user journey, rapidly adapt to evolving fraud patterns, and equip operations teams with the tools needed to investigate and mitigate fraud at scale.

We’re looking for a Senior Software Engineer to join our fully remote team based in Europe. You’ll collaborate closely with stakeholders across North America - including teams in Product, Compliance, Machine Learning, Fraud Operations, Fraud Strategy, and other Fraud Engineering teams.

The Fraud Engineering organization builds the foundational and tactical software that enables affirm to respond strategically to fraud - both in real time and after the transaction. Our mission is to support business growth while protecting affirm, our customers, and our merchants. We evaluate risk at critical decision points in the user journey, rapidly adapt to evolving fraud patterns, and equip operations teams with the tools needed to investigate and mitigate fraud at scale.

The Fraud International Team (FIT) leads the engineering effort to extend affirm's Fraud Decisioning System into markets beyond the US - Canada, the UK, Australia, and growing rapidly. We own real-time fraud decisioning for these markets, integrate region-specific risk vendors, and are building the platform that lets affirm stand up fraud protection in a new country quickly and safely. As affirm expands globally, FIT scales with it.

We're looking for a Senior Software Engineer to join our fully remote team based in Europe. You'll collaborate closely with stakeholders across North America - including teams in Product, Compliance, Machine Learning, Fraud Operations, Fraud Strategy, and other Fraud Engineering teams.

What You’ll Do

• You will own and deliver quarterly goals for your team, leading engineers through ambiguity to solve open-ended problems, and ensuring that everyone is supported throughout delivery.
• You will design and implement real-time fraud decisioning services and APIs in Python or Kotlin, extending affirm's Fraud Decisioning System to markets beyond the US.
• You will build and evolve the platform and tooling that let affirm launch fraud decisioning in a new country quickly—turning market-by-market setup (rules, models, and vendor configuration) into a repeatable, low-friction path so launches scale sub-linearly with the number of markets.
• You will integrate region-specific fraud and risk vendors and help operationalize the machine learning and AI signals that power real-time decisioning, while using modern AI tooling to move faster as an engineer.
• You will support peers and stakeholders across the product development lifecycle - collaborating with Product, Machine Learning, Analytics, and Fraud Strategy, articulating technical constraints, and partnering on decisions that properly weigh risks and trade-offs.
• You will support the operations and availability of your team's systems by creating and monitoring metrics, escalating when needed, and contributing to keep-the-lights-on and on-call efforts.
• You will foster a culture of quality and ownership - setting and improving code review and design standards, mentoring teammates, and leading by example.
• On-Call Rotation - There would be an on-call rotation for this role as a requirement.

What We Look For

• 5+ years of experience building backend systems at scale using Python or Kotlin.
• Experience with distributed systems and infrastructure using AWS, MySQL/PostgreSQL, and Kubernetes.
• Strong system design skills and a track record of delivering maintainable, extensible services.
• Fluency with AI-driven engineering - every affirm engineer builds with tools like Claude Code and most PRs are co-authored with AI, so directing and orchestrating AI and excelling in the reviewer's seat (setting intent, critically evaluating generated code, and owning its correctness, quality, and security) is a core expectation.
• Proficiency in SQL and working with data-rich environments.
• Familiarity with CI/CD practices and safe production deployments.
• Strong written and verbal communication skills, especially in distributed teams.
• A proactive, ownership-driven mindset with a focus on learning and team success.
• Experience with Snowflake, dbt, Airflow, or Chronosphere (nice to have)
• Background in fraud prevention, risk systems, or real-time decisioning (nice to have)
• Experience building for multiple markets or regions - internationalization or localization (nice to have)
• Experience working in the fintech sector or other highly regulated environments, with a strong understanding of risk, compliance, and operational constraints. (nice to have)

Base Pay Grade - N

Equity Grade - 4

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 monthly stipends for health, wellness and tech spending, and benefits (including 100% subsidized medical coverage, dental and vision for you and your dependents). In addition, the employees may be eligible for equity rewards offered by affirm holdings, inc. (parent company).

Additional benefits include:

• Flexible Spending Wallets for tech, food and lifestyle
• Away Days - wellness days to take off work and recharge
• Employee Resource & Community Groups

We are able to offer visa sponsorship for this role, but do require that someone is based in Spain for the role.

Location - Remote Spain

affirm is proud to be a remote-first company! The majority of our roles are remote and you can work almost anywhere within the country of employment. affirmers in proximal roles have the flexibility to work remotely, but will occasionally be required to work out of their assigned affirm office. A limited number of roles remain office-based due to the nature of their job responsibilities.

We’re extremely proud to offer competitive benefits that are anchored to our core value of people come first. Some key highlights of our benefits package include:

• Health care coverage - affirm covers all premiums for all levels of coverage for you and your dependents
• Flexible Spending Wallets - generous stipends for spending on technology, food, various lifestyle needs, and family forming expenses
• Time off - competitive vacation and holiday schedules allowing you to take time off to rest and recharge
• ESPP - An employee stock purchase plan enabling you to buy shares of affirm at a discount

We believe It’s On Us to provide an inclusive interview experience for all, including people with disabilities. We are happy to provide reasonable accommodations to candidates in need of individualized support during the hiring process.

[For U.S. positions that could be performed in Los Angeles or San Francisco] Pursuant to the San Francisco Fair Chance Ordinance and Los Angeles Fair Chance Initiative for Hiring Ordinance, affirm will consider for employment qualified applicants with arrest and conviction records.