Job Title: Senior JavaScript / TypeScript Developer – UI (AI Interfaces) & Excel Add-inLocation: London – (Hybrid)Type: Full-time
About Us: Cornspring is a dynamic start-up developing Family Office services through a unique combination of innovative technology and data management excellence. Our platform leverages state-of-the-art generative AI and large language models to provide unparalleled insights and efficiency to Family Office investment and accounting data.
We pride ourselves on fostering a collaborative and inclusive work environment where we prize creativity, excellence in engineering, a powerful customer focus and attention to problem-solving through great design.
We are seeking an experienced Front-end Developer to join our team, focusing on building our Excel Add-in solutions and web portal platform. You will be responsible for developing sophisticated data manipulation interfaces using TypeScript within the Microsoft Office Add-in ecosystem while also creating intuitive web applications where clients interact with their data using AI. This role requires deep understanding of data visualization, REST API integration, and responsive design principles. You will work closely with our back-end team to ensure seamless integration with our AWS services while delivering exceptional user experiences in both Excel and our React-based web portal.
We’re looking for a Senior JavaScript / TypeScript Developer who thrives at the intersection of elegant UI development and advanced Excel Add-in engineering. Our AI-driven web platform, built using JavaScript, React and TypeScript# Our Excel Add-in, deployed internally within Microsoft 365, integrating directly with our platform APIs
This role is perfect for someone who enjoys building robust user experiences that bridge traditional productivity tools (like Excel) with modern, responsive web apps—and who is excited by the opportunity to work with AI and financial data.
Design, build, and maintain high-performance Excel Add-ins using TypeScript and Office.js, tailored for internal Microsoft 365 deploymentDevelop and scale web interfaces our AI solutions, data visualization, and reportingCollaborate with backend engineers to connect APIs, manage state, and streamline data integrationEnsure excellent UX in both browser and Excel environments, with intuitive, performant, and consistent interfacesSupport cross-team coordination around security, testing, deployment, and CI/CD pipelines
Professional front-end development experience with JavaScript, React and TypeScriptProven experience building and deploying Office Add-ins, especially within Microsoft 365 for internal enterprise useDeep knowledge of the Excel JavaScript API, object models, and data handling within workbook constraintsOAuth), and managing async data interactionsStrong understanding of front-end performance optimization, state management, and cross-environment compatibilityExperience working in Agile teams, with a proactive and ownership-driven mindset
Bonus Points ForExperience with data-intensive applications or financial toolsFamiliarity with data visualization libraries (e.g., D3.js, Chart.js, Recharts)Knowledge of Microsoft Graph API and M365 deployment configurationsExposure to AWS services (Lambda, API Gateway, Cognito, etc.)Understanding of AI and LLM patterns for chat, collaboration or search interfaces
Work with cutting-edge AI and data technologies.Opportunities for professional growth and development.Flexible work hours and remote work options.Engaging and challenging projects that make a real impact to our sector.Bring proven experience in both modern UI development and Excel Add-in engineering in data-centric or enterprise environmentsSend us your CV and (optionally) GitHub/portfolio, along with a short note on your experience with Excel Add-ins, UI development, and what excites you about this role….