Roberto Castellanos

I’m a Senior Full-Stack Software Engineer with 12+ years of experience building, scaling, and maintaining production web applications using JavaScript, React, Node.js, Meteor, and MongoDB.

I specialize in developing end-to-end systems—from clean, responsive user interfaces to robust backend APIs, real-time services, and database architectures. I’ve built and operated full platforms used by real customers, handling authentication, payments, third-party API integrations, and high-availability deployments.

On the frontend, I have a strong eye for UI/UX and extensive experience translating Figma designs into pixel-perfect, responsive interfaces using HTML, CSS, SVG, and animations. I care deeply about performance, usability, and maintainable code.

On the backend, I design and implement scalable APIs, real-time systems using WebSockets, and secure data flows. I’ve also built custom crypto payment systems and automated trading bots using REST and WebSocket APIs (Binance, Kraken), giving me a strong systems and data-driven mindset.

I enjoy working on complex problems, owning features end-to-end, and collaborating with product, design, and engineering teams to deliver reliable, high-quality software. I’m currently open to Frontend, Backend, or Full-Stack Engineer roles where I can contribute immediately and continue growing with a strong engineering team.

I serve as a full-time Senior Full-Stack Software Engineer, responsible for the design, development, deployment, and maintenance of production web platforms used by international customers and partners.

Key Responsibilities & Impact

• Architect and develop end-to-end web applications using JavaScript, Meteor, React, Node.js, and MongoDB
• Design and implement scalable backend systems, including REST APIs, real-time services, authentication flows, and database schemas
• Build and maintain frontend applications with a strong focus on performance, usability, and responsive design
• Translate Figma designs into pixel-perfect UIs, leveraging advanced HTML, CSS, SVG, and animation techniques
• Integrate third-party APIs, payment processors, identity verification services, and external providers
• Develop and maintain real-time systems using WebSockets and event-driven architectures
• Implement security best practices, access controls, and fraud-prevention mechanisms
• Manage deployment pipelines, server environments, and system monitoring to ensure high availability
• Continuously optimize application performance, reliability, and scalability
• Provide technical leadership, code reviews, and mentorship for junior developers when applicable
• Own the full software lifecycle from concept and architecture through production and ongoing support

Technologies Used

JavaScript (ES6+), Meteor, React, Node.js, MongoDB, REST APIs, WebSockets, HTML5, CSS3, SVG, Figma, payment APIs, authentication systems, cloud infrastructure

Universidad Central "Marta Abreu"​ de Las Villas

Bachelor's degree, Biomedical/Medical Engineering