Petar J.

Have an idea and need to turn it into a working MVP quickly? Have a half-built or vibe-coded product that works as a prototype, but needs an experienced engineer to turn it into reliable, production-ready software? Is your existing SaaS product slow, difficult to maintain, or becoming harder to scale? That's where I come in. I'm a Full-Stack Software Engineer with 7+ years of industry experience, a BSc in Computer Science, and a track record of delivering 10+ production applications used by 100K+ users. I take end-to-end ownership - from architecture and technical decisions through implementation, testing, deployment, and production. Throughout my career, I've worked across both startup and enterprise environments, building products in fintech, edtech, e-commerce, social networks, and content subscription - including software for a Fortune Global 500 company. Why work with me? I bring more than a tech stack to a project. I've worked on products at very different stages and scales - from taking new products from idea to MVP, to shipping features in large enterprise systems, to improving SaaS platforms that had already grown complex. Here are a few examples: • I identified a scaling problem and fixed it across an entire fintech product While working on a UK B2B fintech platform, I saw that growing UI inconsistency was making the product increasingly difficult to maintain and extend. I designed and built a shared React npm component library and design system, then helped drive its adoption across the application, transforming 90+ legacy components, increasing development & delivery speed, and reducing maintenance costs. Beyond that, I delivered payment flows including HPP and 3D Secure, authentication and authorization, transaction analytics, onboarding/KYC, CRM, and accounting functionality. • I've shipped software inside a Fortune Global 500 environment I helped digitalize production and quality-assurance workflows between a global fashion company's internal teams and its worldwide supplier network. I built data-heavy product dashboards, production timelines, document and media processing workflows, and a shared npm library that was eventually adopted by 5+ engineering teams across different Micro-Frontends. I independently handled releases, deployments, production monitoring, and post-release investigation for the features I owned. • I've built products from zero, not only worked inside established codebases I've worked on greenfield startup products from the first implementation through beta and built a developer assessment platform, What Is The Output, end-to-end. That means making decisions around product flows, architecture, frontend, backend, database, authentication, testing, deployment, and iteration - not simply implementing predefined tickets. • I've worked on complex, data-heavy products at scale My experience also includes an AI-powered digital enablement platform used by thousands of organizations, where I led frontend development for an advanced analytics experience and built custom D3.js visualizations for large and complex datasets. I've also worked on enterprise accounting software, social and content subscription products, e-commerce, and other SaaS applications. See the actual work: → Case studies, projects, and engineering decisions: petarbuilds.tech/work There you can see examples of the products I've worked on, the problems I was responsible for solving, and how I approached them. What I work with: • Frontend: React, Next.js, TypeScript, JavaScript, Tailwind CSS, shadcn/ui, Radix UI • Backend: Node.js, Express.js, PostgreSQL, MongoDB, Prisma, REST APIs • Architecture: SaaS applications, Micro-Frontends, design systems, component libraries, authentication, API integrations • Quality & Delivery: Vitest, Jest, React Testing Library, Cypress, CI/CD, Docker, GitHub Actions, production monitoring AI-assisted development: Claude, Cursor, GitHub Copilot Whether you're starting with an idea, turning an AI-generated prototype into a production-ready product, or need experienced ownership of an existing SaaS application, let's figure out the best way forward. Send me a message with what you're building, where you are today, and what's holding you back. I'll take a look, and we can discuss the best next step.