Senior Software Engineer, Backend (Post-Purchase International)

About Affirm

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.

Role Overview

Join the pioneering Post-Purchase International team at the forefront of Affirm’s global expansion. You’ll help build the foundational platform and customer experiences needed to bring Affirm’s products to a new generation of international markets. The team owns and evolves the end-to-end post-purchase journey across international markets, ensuring that customers can confidently manage their purchases and access experiences tailored to their local needs. Success requires deep collaboration: you’ll partner closely with European engineering counterparts and teams across Affirm’s global Post-Purchase organization to develop cohesive, scalable solutions.

Responsibilities

• You will be responsible for owning and delivering quarterly goals for your team, leading engineers on your team through ambiguity to solve open-ended problems, and ensuring that everyone is supported throughout delivery.
• You will support your peers and stakeholders in the product development lifecycle by collaborating with product management, design & analytics by participating in ideation, articulating technical constraints, and partnering on decisions that properly consider risks and trade-offs.
• You will proactively identify project, process, technology or business issues, advocate for them, and lead in solving them.
• You will support the operations and availability of your team’s artifacts by creating and monitoring metrics, escalating when needed, and supporting “keep the lights on” & on-call efforts.
• You will foster a culture of quality and ownership on your team by setting or improving code review and design standards for your team, and advocating for them beyond your team through your writing and tech talks.
• You will occasionally contribute to full-stack development, including working on front-end components to help deliver end-to-end features.
• You will help develop talent on your team by providing feedback and guidance, and leading by example.

Total Rewards

We believe the people building honest financial products at Affirm should share in its success. That's why our total rewards are designed to support your health, growth, financial well-being, and future. We reward employees through a combination of base pay, equity (from parent company), and comprehensive benefits.

• Base Pay: 308 000 zł - 428 000 zł.
• Equity: All employees in this role are eligible to receive equity from the parent company each year. Equity Grade: 4.
• Stipends: Flexible spending wallets for technology and wellbeing related needs, reimbursable up to 1390 zł per month.
• Time Off: Competitive paid time off, paid public holidays, and additional paid Away Days.
• Healthcare: Comprehensive private healthcare through Lux Med's Platinum package. We cover 100% of premiums for employees and their dependents.
• Well-being: A MultiSport card, mental well-being support through Lyra (up to 12 confidential counseling or coaching sessions per year), and financial well-being support through Northstar.
• Growth: Learning and development programs.
• Family Support: Family healthcare support through Maven and parental leave support through Parentaly.
• Culture: Employee Resource Groups (ERGs) that foster connection and inclusion.
• Stock: Employee stock purchase plan (ESPP) lets you buy Affirm stock at a discount.
• Flexibility: Remote-first company.

Requirements

• 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 are enthusiastic about occasionally working on front-end code (no prior front-end experience is required).
• 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.

Bonus

• You’ve had exposure to building web apps with declarative UI frameworks (e.g., React or Vue) and understand the core principles behind them.