In this episode of Señors @ Scale, Eric Rasmussen — creator of Redux Form and React Final Form, now Principal Product Engineer at Attio — joins Dan to talk about building open source at scale, developer experience, and the lessons learned from two decades of shipping frontend software.Eric shares his journey from early experiments with BASIC and FoxPro to designing Attio’s secure SDK ecosystem, which enables third-party developers to extend a next-generation CRM. Along the way, he opens up about the pitfalls of feature creep in open source, the evolution from Redux Form to React Final Form, and how AI is already reshaping documentation.We dive into why developer ergonomics matter more than ever, how strict design systems preserve product quality, and what it really takes to manage breaking changes when your code runs in thousands of apps. Eric also offers practical advice for juniors looking to break into open source, as well as insights on testing strategies, state machines, and the libraries he can’t live without.🎯 Whether you’re maintaining a popular open source library, building SDKs for other developers, or just curious about the hidden costs of “yes” in software design, this conversation is full of hard-won lessons from the trenches.Chapters00:00 Introduction to Eric Rasmussen and His Journey05:34 Early Programming Experiences and First Job08:01 Transition to Principal Engineer at Atio10:37 Understanding Atio's CRM and Its Market Position13:08 Developer Experience and Building for Other Developers15:29 The Role of Documentation in Developer Tools18:03 SDK Development and Framework Choices20:30 Building a Secure and Custom Runtime22:54 Managing Breaking Changes and Developer Feedback25:28 The Creation of Redux Form and Its Impact27:59 Testing Strategies for SDKs and Components33:48 Building a Design System35:27 React Final Form: Evolution and Insights41:11 The Journey from Redux to React Final Form46:08 Choosing State Management Solutions48:10 Overused Libraries and Tools54:25 Advice for Junior Developers59:32 Book Recommendations and Closing Thoughts01:04:25 OutroFollow & Subscribe:📸 Instagram: https://www.instagram.com/senorsatscale/📸 Instagram: https://www.instagram.com/neciudev🎙 Podcast URL: https://neciudan.dev/senors-at-scale📬 Newsletter: https://neciudan.dev/subscribe💼 LinkedIn: https://www.linkedin.com/in/neciudan💼 LinkedIn: https://www.linkedin.com/company/se%C3%B1ors-scale/#opensource #reduxform #reactfinalform #frontend #developerexperience #sdk #documentation #designsystems #softwareengineering #señorsatscale #techtalks #webdevelopmentDon’t forget to like, comment, and subscribe for more engineering stories from the front lines. What’s your favorite open source library — and how has it shaped your work? Share below 👇Don’t forget to like, comment, and subscribe for more engineering stories from the front lines.