Stephen Jay

Available to hire

Hi, I'm Stephen Jay, a Full-Stack & Mobile App Developer, Software Engineer, and UI Designer based in Berlin.

About

Hi, I’m Stephen Jay, a Full-Stack & Mobile App Developer, Software Engineer, and UI Designer based in Berlin. I specialize in building complete, end-to-end digital solutions—from intuitive user interfaces to scalable back-end architectures.

What I Do:
• Full-Stack & Web Development: Custom web apps, robust APIs, database design, and seamless CRM integrations (Salesforce, HubSpot, custom workflows).
• Mobile App Development: Cross-platform mobile applications optimized for performance, security, and smooth user experience.
• UI/UX & Web Design: Crafting clean, responsive user interfaces and modern web layouts that engage users and drive conversions.

Whether you need a brand-new application built from scratch, custom API/CRM integrations, or a complete UI revamp, I deliver clean, maintainable code on time and within budget.

Let’s discuss how we can bring your next project to life!

  • 4 years' experience
  • Joined October 2026

Languages

  • GermanFluent
  • EnglishFluent
  • Spanish; CastilianFluent
  • ItalianFluent

Industry experience

  • Computers & Electronics
  • Financial Services
  • Software & Internet
  • Media & Entertainment
  • Consumer Goods
  • Gaming
  • Education

More experts in Berlin, Germany

Work experience

Mobile App & UI Engineer · AppCraft TechAug 2024 – May 2026 · 1 yr 10 mos

Developed cross-platform mobile applications using React Native and Flutter. Focused on frontend design, custom UI components, API connectivity, and performance optimization across iOS and Android platforms.

Full-Stack Developer · TechSolutions BerlinMay 2022 – Nov 2023 · 1 yr 7 mos

Engineered scalable web applications using React, Node.js, and PostgreSQL. Developed RESTful APIs and integrated third-party CRM automation pipelines. Collaborated with design teams to translate Figma prototypes into pixel-perfect, responsive interfaces.

Senior Full-Stack & Mobile App Developer · Self-Employed / FreelanceFeb 2022 – Present · 4 yrs 10 mos

Delivering custom web and mobile development solutions for global clients. Specialized in React Native, Node.js, and API integrations. Built cross-platform mobile apps, designed scalable databases, integrated CRM systems (HubSpot/Salesforce), and crafted responsive UI components.

Education

Bachelor of Science in Computer Science · Technische Universität Berlin (TU Berlin)2018 – 2022

Focused on software engineering, object-oriented programming, database systems, web technologies, and mobile application development. Graduated with a focus on full-stack architecture and interactive user interfaces.

Master of Science in Computer Science · Humboldt-Universität zu Berlin2022 – 2024

Advanced specialization in distributed software systems, mobile computing, web engineering, and UX design optimization.

Certifications and awards

Meta Front-End Developer Professional Certificate2024

Comprehensive 7-month program covering React, HTML5, CSS3, JavaScript, UI/UX design principles, and responsive web application development.

AWS Certified Developer - Associate2023

Demonstrates proficiency in developing, deploying, and debugging cloud-based applications using AWS services, RESTful APIs, and serverless architecture.

Meta Android Developer Professional Certificate2025

Focused on mobile application lifecycle, Kotlin/Java, mobile UI components, API integration, and cross-platform app performance.

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