Senior Full-Stack Engineer - Onboarding (SDK)

ABOUT THE ROLE Taktile helps financial institutions make smarter, safer decisions with the power of AI. Our software gives teams the tools to automate complex decisions, from customer onboarding and underwriting to fraud detection, with full visibility and control. By combining AI with a rich ecosystem of financial data, we enable companies to adapt their decision-making in real time as markets, customer behavior, and risks evolve. 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. This is a high-impact, high-ownership role with a clear path to leading the team as it grows. If you've built SDKs, shipped embeddable components, or worked on developer-facing products that run in other people's browsers, and you're excited about doing it again at the intersection of fintech and platform engineering, we'd love to talk. 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. REQUIREMENTS - Hybrid role based in Berlin or London. We collaborate in person regularly and don't offer remote-only for this position. - Fluent English required. You'll write design docs, review PRs with context, and occasionally join customer calls. - Strong engineering fundamentals across the full stack: you're equally comfortable designing clean APIs and building responsive, accessible front-end experiences. - Deep understanding of how browsers work: the DOM, security models (CSP, CORS, iframe sandboxing), caching, script loading, and performance. - Comfortable operating systems in production and participating in incident response as part of a team rotation. REQUIRED EXPERIENCE - 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. You know what it takes to version, distribute, and support code that runs in environments you don't control. - Production experience with TypeScript/JavaScript on both client and server. You've built modern front-end applications and understand bundling, tree-shaking, and cross-browser compatibility deeply. - Experience with iframe-based architectures, postMessage communication, and sandboxed execution environments. - Proficient in backend development (Python is a plus), you can build the APIs and configuration services that power the SDK. - Prior industry experience with public cloud providers (preferably AWS). IDEAL, BUT NOT REQUIRED - Experience in identity verification, fraud prevention, or fintech - you've worked with providers like Socure, Vouched, Onfido, Fingerprint, or ThreatMetrix. - Familiarity with media APIs (camera access, image capture, WebRTC) and the nuances of build