Software Engineer II, Frontend (Purchasing Integrations)

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. 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 oper...