Software Engineer II, Frontend Purchasing Integrations

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 Purchasing Integrations team is responsible for the JavaScript SDK and frontend infrastructure that power Affirm at checkout. We build the library that merchants embed directly into their storefronts - rendering payment messaging and buttons, initiating checkout flows, and orchestrating secure, real-time communication with Affirm’s web app. This code runs on high-traffic production sites, so performance, resiliency, and backward compatibility are critical. Milliseconds matter, and failure is immediately visible to merchants and consumers.

This role is deeply frontend-focused. Engineers work on bundle optimization, script loading strategies, rendering performance, and Web Vitals, ensuring our SDK integrates cleanly into diverse merchant stacks without degrading UX. We design extensible UI components that support evolving checkout experiences while keeping integration simple and incremental for developers. Security enhancements and modern browser-based communication patterns are core to the work.

The team operates at the intersection of platform and product: building reusable primitives, experimenting with new checkout surfaces, and translating complex requirements into intuitive APIs and polished UI. It’s an opportunity to work on high-scale frontend systems embedded across the web—where engineering rigor directly impacts conversion, growth, and user experience.

What You'll Do: · With the support of your team’s tech lead and manager, you will break down larger projects into individual tasks, deliver them in multiple phases, and collaborate with others to ensure timely delivery of your work. · 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 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 contribute to a sense of community on your team by engaging in growth and development activities such as participation in the interview process. What We Look For: · You have a total of 1.5+ years of experience as a software engineer. · You have experience shipping web apps using declarative UI frameworks like React or Vue. · You have experience working with Javascript/Typescript. · You have experience designing, developing and launching APIs at scale using languages like Python or Kotlin. · You have mastered taking a simple problem or business scenario into a solution that interacts with multiple software components, and executing on it by writing clear, easily understood, well tested