Senior Full-Stack Engineer - Onboarding (SDK)

About the role

We're looking for a Senior Full-Stack Engineer to be a founding member of the Web SDK team and help shape this product from the ground up. You'll own the architecture of a unified client-side SDK that abstracts identity verification, device intelligence, and document capture behind a single, elegant integration, used by financial institutions to onboard customers securely and seamlessly.

What you'll do

• Architect the SDK from scratch: Design and build a client-side JavaScript/TypeScript SDK that orchestrates multiple third-party vendor scripts behind a unified, headless API
• Build the hosted verification experience: Create a secure, embeddable web application that renders interactive identity verification flows with a polished, brandable UX
• Own reliability end-to-end: Establish versioning strategies, staged rollouts, and CI/CD pipelines for client-side code that runs in customer browsers
• Solve hard integration problems: Wrangle vendor SDKs that each have their own quirks, lifecycle hooks, and failure modes, and make them work together seamlessly
• Shape the product and the team: Collaborate with Product, Design, and customers to define the SDK's developer experience. As the team grows, you'll have the opportunity to step into a tech lead role
• Work directly with customers: Engage with early adopters to understand their integration environments and ensure the SDK works flawlessly in the real world

What you'll need

• 5+ years of professional software engineering experience
• At least 2 years building and shipping a client-side SDK, embeddable widget, or developer-facing JavaScript library used by external consumers
• Production experience with TypeScript/JavaScript on both client and server
• Experience with iframe-based architectures, postMessage communication, and sandboxed execution environments
• Deep understanding of how browsers work: the DOM, security models (CSP, CORS, iframe sandboxing), caching, script loading, and performance
• Proficient in backend development (Python is a plus)
• Prior industry experience with public cloud providers (preferably AWS)
• Hybrid role based in Berlin or London

Nice to have

• Experience in identity verification, fraud prevention, or fintech
• Familiarity with media APIs (camera access, image capture, WebRTC)
• Experience building developer tools, documentation, or SDKs with a focus on great developer experience
• Previous experience as a tech lead or strong desire to grow into one
• Knowledge of security and compliance considerations (SOC2, PII handling) for client-side applications

What they offer

• Top-of-market equity and cash compensation package
• Self-development budget for conferences, books or classes
• New Apple MacBook Pro and meaningful home office set-up
• Flat hierarchy with direct communication to founding team members
• Learning from experienced mentors and network of leading tech investors