Sébastien Ballesteros

• Led the (incremental) rewrite of DuckDuckGo's search engine result page (and testing infrastructure) in React and drove cultural change through software choices, resulting in higher engineer productivity (as measured by Google's Goal Signal Metrics framework).
• Used those new foundations (and associated tooling) to drive the adoption of a design system.
• Led several web performance optimization projects (e.g., web vitals tracking and optimization) that resulted in a significant increase of the company's core engagement and revenue metrics.
• Led various fast-paced projects (using build/measure/learn cycles and working closely with product and design teams) that successfully improved the adoption and retention of DuckDuckGo's products (as measured by online controlled experiments and A/B testing).
• Identified key areas of improvement through the development of internal tools and applications to evaluate and monitor the performance of DuckDuckGo's search products.
• Drove the adoption of multiple new technologies (e.g., Next.js).
• Gained ownership and contributed to multiple areas of the code base (e.g., online controlled experiments framework, search engine result page, local search, browser extensions).

• Led the development and release of the frontend (React) and backend (Node.js / NoSQL Database) of a new product collecting reviews on preprints relevant to the Outbreak Science community, in close collaboration with product managers and design.
• Identified an opportunity to develop a browser extension for the product to better serve user needs at minimal cost and complexity (large code-reuse); and led its successful development and release.

• Earned acceptance to and completed Techstars NYC, Mozilla webFWD and Tigerlabs (Princeton) programs (the company was also known as Standard Analytics and science.ai).
• Helped major scholarly publishers to successfully transition from an XML/print-first workflow to an HTML/web-first one.
• Architected and built a complex React/Redux application (collaborative task completion, roles management, real-time updates, offline support, rich text editing, annotations, payments, first-class support for print).
• Designed and built a hypermedia API (and associated data model) based on schema.org actions.
• Architected and built a document transformation service (OOXML to HTML, image resizing, video transcoding).
• Built a CI/CD pipeline and deployed and monitored the application on AWS.

Work samples: science periodicals GitHub organization, Twitter threads (1, 2)