” ... he's one of the most technically sharp engineers I've collaborated with. Their depth of knowledge across technologies was consistently impressive, they could navigate complex challenges with both speed and clarity ... ”
Hi, I'm Javier Machín.
Senior Software Engineer.
Learn more about meAbout Me
I'm Javier, a product-minded Senior Software Engineer with over 8 years of professional experience, 7 of them fully remote across US, Swedish, German, and Spanish teams.
I bridge the gap between complex business requirements and high-performance technical implementation. By partnering closely with product and design, I ship scalable solutions that drive measurable business outcomes (such as improved conversion, cost reduction, and performance optimization), always balancing speed, quality, and user needs.
My Stack & Process:
- Front-end: React, Next.js, TypeScript, and Tailwind CSS.
- Mobile: React Native (Expo).
- Back-end & Data: Node.js (NestJS, Next.js API routes, Express, Fastify), Prisma, and PostgreSQL.
- Modern Workflow: I leverage AI-augmented development to accelerate delivery cycles and increase productivity, backed by a strict manual audit process. This ensures all code meets senior-level standards for security, scalability, and maintainability.
I have a proven track record of leading teams through complex and ambiguous challenges. I mentor developers, align engineering efforts with clear business goals, and help teams collaborate effectively under uncertainty.
My portfolio includes projects delivered to names such as Paradox Interactive, Grover, and Insendi.
Outside of the tech world, I'm an avid car and motorcycle enthusiast, and I enjoy the beautiful island of Lanzarote, my current home.
Let's connect and explore how I can help turn your business goals into shipped product.
Professional Projects
Ukio
Worked for the proptech Ukio, a company that specializes in offering fully furnished, design-forward apartments for monthly stays through a digitized customer experience.
Key Contributions & Impact:
- Spearheaded the migration of legacy features to a new, high-performance application, directly boosting PageSpeed scores by over 20%.
- Architected cost-saving optimizations for Vercel and Sanity CMS by leveraging CDNs and improving queries, slashing hosting costs by more than 50%.
- Engineered the company's primary mobile app from ideation to launch, managing the entire process including implementation in React Native and publishing to the Apple and Google Play Stores.
Tech Stack: React, React Native, TypeScript, Next.js, Zod (data validation), Zustand (state management), Sanity CMS, Tailwind, Vercel, AWS (Elastic Beanstalk).
Grover
I was directly involved in the creation of the B2B side of the German unicorn Grover. With over $2.2B raised, Grover makes technology accessible to everyone by enabling them to subscribe to tech products monthly. I worked on the B2B front-end, architecting and implementing features to drive business growth.
Key Contributions & Impact:
- Enhanced the B2B user registration flow, implementing UX improvements and A/B testing which increased the conversion rate by 20%.
- Championed and integrated Cypress end-to-end testing into the team's CI/CD pipeline, significantly reducing the number of bugs reaching production.
- Mentored and onboarded new engineers through a buddy program, improving team cohesion and ramp-up speed while maintaining all development responsibilities.
Tech Stack: TypeScript, Next.js, React, GraphQL, Cloudfront (Micro-frontend routing), Cypress.
Insendi
Worked on the development of the successful digital learning platform Insendi, which provides universities such as Imperial College London, ESMT Berlin, University of Melbourne, Johns Hopkins Carey Business School, and HKUST the ability to create engaging online courses. Insendi was acquired by StudyGroup in 2020. My role was to build interactive learning activities and enhance the user experience for both students and educators.
Key Contributions & Impact:
- Proactively improved platform stability by addressing client pain points and shipping targeted code fixes, which significantly reduced live support requests and operational costs.
- Acted as a technical subject-matter expert (SME) alongside the CTO in key client meetings at Imperial College London, helping secure and strengthen university partnerships.
- Led the migration of legacy learning activities to a modern and more performant Next.js application, enhancing reliability and the end-user experience.
Tech Stack: React, Redux, Next.js, JavaScript, Enzyme.
Beatroot
Directly involved in the development of the music distribution application Beatroot, part of the Tennessee-based music corporation Made in Memphis, founded by Hall of Fame musician David Porter. My work involved improving front-end performance and leading the effort to develop and implement a new, modern UI for the platform.
Key Contributions & Impact:
- Developed a key monetization feature enabling the creation of song clips for social media platforms like TikTok, opening up new revenue streams for artists.
- Engineered a new multi-part file upload system with pause/resume functionality, slashing asset upload times by 40% and dramatically improving the user experience for music distributors.
- Led the complete redesign and development of the application's UI using React and Redux, achieving 95% test coverage and significantly reducing application crashes.
Tech Stack: React, Redux, TypeScript, JavaScript, Ruby on Rails.
Consulting
Through the Swedish agency Odd Camp, I provided consulting and development services for multiple high-profile clients, building bespoke web products tailored to their unique needs. Clients Included: Paradox Interactive, Naturkartan, and Blendow Lexnova.
Key Contributions & Impact:
- Designed and built a promotional WebGL and VR-compatible game for the launch of 'Wraith: The Oblivion - Afterlife,' which received multiple industry accolades.
- Executed the front-end implementation for the 2021 redesign of the official website for the multi-million selling game 'Cities: Skylines.'
- Drove a 30% reduction in client hosting costs by architecting and implementing more efficient technology stacks, boosting both performance and developer productivity.
Tech Stack: React, Next.js, TypeScript, JavaScript, Ruby on Rails, Gatsby (static site generation), A-Frame (WebGL and VR framework).
Featured Project
Public AI Service
A live, public, no-sign-up AI web app that turns a free-text description into an illustrated story.
The interesting engineering wasn't generating the story, it was running a generative-AI service on the open internet without a drained API budget or unmoderated output. I designed it around the open-access, cost, and abuse trilemma, landing on a secure, well-behaved service that runs at a fraction of a cent per story at any scale.
Read the full case study: Shipping a Public AI Service Without Going Broke
Key Engineering Decisions:
- Drove per-story cost to roughly half a cent at any scale by routing all language work (input parsing, narrative, and image prompts) through a single free open model and paying only for image generation, with prompts and parameters tuned to get a usable result on the first try.
- Protected the budget on an open, account-less service with a Redis-backed rate limiter keyed on the anonymous visitor, so it stays abuse-resistant without a sign-up wall.
- Hardened a public generative endpoint against malicious or garbage input and inappropriate output, using input validation plus an LLM moderation pass that balances creative freedom with content safety.
- Tamed AI non-determinism (the core engineering challenge) by combining prompt engineering, tuned generation parameters, and robust error handling, so unpredictable model output degrades gracefully into reliable, structured UI data instead of crashing.
- Matched storage to data lifetime: Redis for ephemeral rate-limit counters, Supabase (Postgres) for a durable blacklist of repeat abusers, plus analytics to spot abuse and guide improvements.
Try it out: magicaistory.com
Tech Stack: Next.js, TypeScript, LLM / AI Image Generation APIs, React, Tailwind, Vercel, Redis (rate limiting), Supabase (Postgres for blacklist).
Testimonials
” ... I had the pleasure of working with Javier and was always impressed by his professionalism and technical skills. He has a great ability to anticipate problems before they escalate, offering solutions that save time and improve the final outcome ...”
“ ... No matter the project, he never hesitated to take it on and deliver outstanding results. Javier is not only a skilled front-end developer but also a true team player, always willing to lend a hand and contribute to the team's success ... ”
“ ... During our period working together we went through multiple pair-programming sessions, investigating issues, discussing project proposals and I can only mention that all of them were really joyful ... ”
“Javier was quick to jump into various projects that we worked on at Odd Camp, ranging from Gatsby to Ruby on Rails. If anything was thrown his way he would gladly do it and do it well. He was amazing to work with and I would gladly work with him again.”
“ ... Within a few months in the role, he adapted really well to our fully remote working culture and demonstrated his abilities conceiving solutions that fulfill business needs ... ”
“ ... Javier is one of the most driven people I've had the pleasure to work with. Upon joining the team he didn't hesitate to throw his self in to solving the more difficult bugs which had plagued the team for some time ... ”
“ ... He was leading the development of the frontend application, leaving the application in a much better shape than it was before he joined the team and increasing the test coverage by a big margin ... ”
” ... he's one of the most technically sharp engineers I've collaborated with. Their depth of knowledge across technologies was consistently impressive, they could navigate complex challenges with both speed and clarity ... ”
” ... I had the pleasure of working with Javier and was always impressed by his professionalism and technical skills. He has a great ability to anticipate problems before they escalate, offering solutions that save time and improve the final outcome ...”
“ ... No matter the project, he never hesitated to take it on and deliver outstanding results. Javier is not only a skilled front-end developer but also a true team player, always willing to lend a hand and contribute to the team's success ... ”
“ ... During our period working together we went through multiple pair-programming sessions, investigating issues, discussing project proposals and I can only mention that all of them were really joyful ... ”
“Javier was quick to jump into various projects that we worked on at Odd Camp, ranging from Gatsby to Ruby on Rails. If anything was thrown his way he would gladly do it and do it well. He was amazing to work with and I would gladly work with him again.”
“ ... Within a few months in the role, he adapted really well to our fully remote working culture and demonstrated his abilities conceiving solutions that fulfill business needs ... ”
“ ... Javier is one of the most driven people I've had the pleasure to work with. Upon joining the team he didn't hesitate to throw his self in to solving the more difficult bugs which had plagued the team for some time ... ”
“ ... He was leading the development of the frontend application, leaving the application in a much better shape than it was before he joined the team and increasing the test coverage by a big margin ... ”
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