Senior Software Engineer, Frontend

Affirm

Location: Spain
Job Type: full-time
Salary: €85,000 - €115,000
Posted: January 3, 2026

Job Description

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.

As part of the Checkout Experience team, you'll be responsible for maintaining UIs and APIs that power the delightful user experiences at the core of all Affirm checkout experiences.
We maintain UIs and APIs that power the delightful user experiences at the core of all Affirm checkout experiences. You will be working alongside multiple partner teams across US and Europe to support feature development as well as moving the dial on key metrics that help us ensure Affirm users are able to pay in the way they want, without harming their financial health.

What You'll Do

· 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 help develop talent on your team by providing feedback and guidance, and leading by example.
· On-Call Rotation - There would be an on-call rotation for this role as a requirement.

What We Look For

· You have 4+ years of experience of developing and architecting web applications using declarative UI frameworks like React or Vue.
· You are proficient in JavaScript/TypeScript. Familiarity with backend technologies like Kotlin or Python is a plus.
· 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.

Compensation & Benefits

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).

ESP base pay range per year: €85,000 - €115,000

Additional benefits include:

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

Location - Remote Spain

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

#LI-Remote

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.

🎯 Who is this job for?

This role is well-suited for a senior frontend engineer who wants to own major product initiatives within a high-impact checkout experience, working across global teams to design and deliver scalable UIs in React/TypeScript while influencing architecture, quality standards, and operational reliability. It fits someone experienced in large codebases, comfortable navigating ambiguity, collaborating closely with product and design, mentoring peers, and driving measurable improvements in complex, user-facing financial flows.

💬 Potential Interview Questions

What frontend technologies are you strongest with for building checkout experiences?
React and TypeScript as my primary stack, with experience building high-traffic, multi-step checkout flows, state management (Redux/RTK or Zustand), and integration with payment APIs and risk/eligibility services.
How have you contributed to architecting or evolving large web applications?
I’ve led design for significant features by defining component boundaries, data flows, and contracts with backend services, writing RFCs/tech specs, and driving incremental rollouts behind feature flags to keep changes safe in a large codebase.
Describe your experience working with APIs in a checkout or transaction-heavy context.
I’ve integrated multiple backend services (eligibility checks, payment execution, risk/fraud, promo calculation) via REST/GraphQL, handling retries, idempotency, and granular error states so users always see clear next steps without duplicate charges.
How do you ensure reliability and performance for critical flows like checkout?
I treat performance and reliability as features: measure with RUM and synthetic tests, optimize bundle size and critical path, use graceful degradation for non-essential elements, and add robust monitoring/alerts on key funnel metrics and error rates.
What’s your experience leading through ambiguity and setting technical direction?
I’ve owned quarterly-sized projects where the problem wasn’t fully defined, collaborated with product/analytics to clarify goals and KPIs, proposed a phased technical plan, aligned stakeholders, and led the team through delivery with regular checkpoints.
How do you work with product, design, and analytics on user-facing features?
I join early ideation, surface technical constraints and edge cases, co-define success metrics (conversion, drop-off points, latency), prototype quickly, and then iterate based on A/B tests, user feedback, and data from the funnel.
What is your experience with on-call and “keep the lights on” responsibilities?
I’ve participated in on-call rotations for high-traffic apps: triaging incidents, rolling back or hotfixing safely, communicating impact, and afterward driving RCA, playbooks, and preventive improvements so the same issue doesn’t recur.
How do you handle making significant changes in a large existing codebase safely?
I rely on strong test coverage, feature flags, small incremental PRs, and careful dependency mapping. I start by tightening tests around the area, then refactor in steps, keeping behavior identical while improving structure and isolating risk.
How do you foster a culture of quality and ownership on your team?
By modeling high standards in my own code and reviews, clarifying “definition of done” (tests, monitoring, docs), encouraging engineers to own features end-to-end (from design to metrics), and giving direct, constructive feedback that helps people grow.
Why are you interested in the Senior Frontend Engineer role on Checkout Experience International at Affirm?
It combines what I care about most: mission-driven fintech, critical checkout flows, and international user experience. I enjoy building trustworthy, performant UIs where small improvements have huge impact on conversion and user financial health, and Affirm’s focus on transparent credit aligns strongly with my values.

📋 Job Summary

Affirm is hiring a Senior Software Engineer, Frontend (Checkout Experience International) (Remote, Spain) to own and evolve the React/TypeScript UIs (and related APIs) that power core checkout experiences across US and Europe, leading delivery on quarterly goals, driving technical design in a large codebase, collaborating closely with product, design, and analytics, and supporting reliability through metrics, on-call, and “keep the lights on” work. You’ll architect and ship scalable, extensible web features, mentor peers, improve code review and design standards, and help optimize key business metrics, with bonus points for experience in backend tech like Kotlin or Python. The role requires 4+ years building and architecting web apps with declarative UI frameworks (React/Vue), strong communication and ownership, and comfort working through ambiguity. Compensation for Spain is €85,000–€115,000 base + equity, plus fully subsidized medical, dental and vision for you and dependents, flexible spending wallets (tech/food/lifestyle), wellness “Away Days,” L&D programs, parental benefits, employee communities, and fully remote work within Spain with visa sponsorship available.