Sophia Castillo

Full-Stack

Engineer

I help entrepreneurs, content creators, and businesses turn their ideas into something extraordinary. Operating out of D.C., I team up with clients to whip up smart code and stunning designs. Let’s make something awesome together—working with me means you get a partner who’s all about creating cool stuff and seeing results. Pinky swear!

hi@builtbysophia.com

Currently working remotely from Washington, D.C.

My journey as a software engineer started in a very unexpected way. I began my career as an actor, where I fell in love with storytelling, creativity, and human connection. Just like in acting, web development demands discipline, curiosity, and constant learning — and that’s what pulled me in. Now, I bring that same creative energy into my work as a developer, blending imagination with technical skill.

Languages: JavaScript, TypeScript, Dart, Python

Frontend: React.js, Next.js, React Native, Flutter, Tailwind CSS

Backend: Node.js, Express.js

Databases & Auth: Firebase, MongoDB, NoSQL

Cloud & DevOps: AWS

Suprise!

Hi I'm Joey! I love to appear on my human's video-calls. She always tries to be professional with clients, but I do love to surprise her.

What I Offer

💻

Custom Design & Development

Modern, responsive websites designed to reflect your brand and drive results.

Fast, SEO-optimized, and mobile-friendly
Built with performance and scalability in mind
Includes tools like CMS, booking systems, and more

🛍️

Shopify & Squarespace E-Commerce

I build beautiful and functional online stores that convert visitors into loyal customers.

Custom Shopify storefronts using Storefront API
Squarespace setup and customization
Product pages, checkout flows, and style alignment

📱

Mobile App Development

From concept to launch, I build cross-platform mobile apps.

iOS & Android apps from a single codebase
Great for small businesses, startups, or content creators
UI/UX focused and performance-optimized

🔧

Website Refreshes & Maintenance

Sometimes you don’t need a full rebuild — just a little love and a few intentional tweaks.

Monthly updates and fixes
Light branding support: fonts, colors, Canva templates
Content updates and technical support

Working with Sophia was an absolute delight! She effortlessly brought my hair extensions website to life with her unparalleled expertise and creativity. The end result? A charming and stunning online space that truly reflects the essence of my business. I can't thank Sophia enough for her professionalism, patience, and unwavering commitment to excellence throughout the entire experience.

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Breanna Calle, Owner at Carousel Hair Extensions

We contracted with Sophia for React Native front-end iOS app development and she did a great job. Sophia has excellent communication and collaboration skills and was very easy to do business with. I hope to work with Sophia on more projects in the future...

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Marc Kase, Fractional CIO & CTO at Achieve Agility, Inc.

I highly recommend Sophia as a front-end, React Native web developer. Her expertise in React Native and dedication to delivering high-quality code significantly contributed to the success of our projects at Kaptain. Sophia is a skilled developer, proactive problem solver...

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Kirk Magnuson, Founder & CEO at Kaptain Outside App

She delivered professional level code on the back and front end of the project while contributing creatively to the scope. Her eye for detail and design were key throughout the development process. She delivered professional level code on the back and front end of the project while contributing creatively to the scope. Her eye for detail and design...

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Ryan Braun, Senior Associate Technical Consultant at AHEAD

The great developers don't become great entirely by themselves, and Sophia's humility is what I admire most about her. We need more professionals like Sophia. She did not have any technical background going into the bootcamp, but she showed tremendous growth throughout the course, and to this day continues to hone her skills and astonish me...

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Chad Tao, Senior Software Engineer at Populus Media

It was an absolute pleasure working with Sophia. I appreciated her can-do attitude, her flexibility, and her intuitive nature. All members of our foundation were always pleased with the work she produced. Thank you again.

Juanita Holley, Board Member at Newport Beach Arts Foundation

I chose to work with Sophia on multiple web design projects because she is a studious coder, steadfast teammate, intelligent contributor, and a joy to work with. We also went through a rigorous process together of learning multiple coding technologies, libraries, and web design tenets...

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Kevin Miller, Full-Stack Web Developer & Chemist at Agilent Technologies