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Most AI apps demo beautifully — then break the moment real users and real payments hit them. Subscriptions that double-charge, webhooks that silently fail, billing that collapses on the first edge case. I build the part that has to actually work. I'm a full-stack developer focused on Stripe payments and production-grade AI apps on Next.js + Supabase. Bring me an idea or a half-finished product, and I ship the version that holds up when money and users are real. What I handle end to end: — Stripe: subscriptions, metered/usage billing, Connect, Price IDs, webhooks, affiliate & usage tracking — AI features: OpenAI/Claude integrations, RAG, AI workflows wired into a real product — Full stack: Next.js, TypeScript, Supabase (Postgres, RLS, Auth), Vercel — Auth, multi-tenancy, and the unglamorous production glue that keeps it all from breaking Selected results: — PropRadar — AI property-comparison platform (Next.js + Supabase). 5★, "technically very strong." — Stripe Checkout with Price ID + affiliate tracking, plus a full subscription billing dashboard. — AI website generators for B2B. 5★, "exceptional, high-performance." How I work: fixed-price with clear milestones. Instead of jumping on a call, I'll send you a deployed demo so you can judge the quality up front. Glad to start with a small paid task.

👋 Hi, I'm Julia from Koitechs - Top Rated Plus Upwork team focused on React, Next.js, Node.js, React Native, TypeScript, Supabase, PostgreSQL, and AI product development. My main goal is save up to 40% of our budget to get a market-ready, stable and scalable product. I help companies hire in-house, CTO-approved engineers who join fast, take ownership, and deliver production-ready software. ✅ 9+ years in software development ✅ 155+ web and mobile projects delivered ✅ 20,500+ Upwork hours in React / Next.js / Node.js / React Native ✅ 75% repeat clients ✅ Engineer matching in 24 hours or less ✅ 2-week trial period ✅ 35+ in-house engineers ✅ 40+ MVPs released ✅ Products supported by our team include platforms with 5M+ daily users 🚀 React / Next.js / Full Stack We build SaaS platforms, marketplaces, dashboards, admin panels, CRMs, AI products, and scalable web apps using React, Next.js, Node.js, TypeScript, Supabase, PostgreSQL, Firebase, MongoDB, REST API, GraphQL, Stripe, OAuth, WebSockets, AWS, Vercel, and Docker. Our team is a strong fit if you need a react developer , web developer , full stack developer , nextjs developer, mern developer, or backend engineer. We help with MVP development, legacy code takeover, architecture modernization, Core Web Vitals, API integrations, payments, auth, subscriptions, user roles, and production launch. 📱 React Native / Mobile We build and support iOS and Android apps using React Native, Expo, Firebase, Supabase, Node.js, and API-driven architecture. We can help if you need a react native developer , mobile app developer, iOS / Android support, app takeover, mobile maintenance, push notifications, App Store / Google Play releases, payments, or backend integrations. We also support mixed mobile environments with flutter developer , android developer , backend developer, AI developer, or web developer. 🤖 AI SaaS / AI App Development We build AI-powered products connected to real business workflows. Experience: AI SaaS, AI MVPs, AI chatbot development, AI agent development, OpenAI API, Claude API, LLM prompt engineering, RAG, automation, web scraping, AI model integration, copilots, and AI workflow validation. AI stack: OpenAI API, Claude API, LLMs, RAG, AI Agent Development, AI Chatbot, Generative AI, Python, FastAPI, Supabase, PostgreSQL, pgvector, automation, data analysis, web scraping. 🧩 Mixed-Stack Support Our core focus is React, Next.js, Node.js, React Native, TypeScript, Supabase, and AI. We also support products involving wordpress , vue , angular , python developer , scala developer , flutter developer , android developer , mern , and other web/mobile technologies. 🏆 Industries 📦 Logistics - 5+ projects: tracking, shipment dashboards, carrier/shipper workflows, maps, route visibility. 🏥 HealthTech -4+ projects: medical booking, clinic platforms, patient flows, admin systems. 🛒 Marketplaces & E-commerce - 15+ projects: multi-vendor products, Stripe, subscriptions, bidding, complex search. 🏠 PropTech / Real Estate -5+ projects: listings, booking flows, agent dashboards, rental platforms. 🤖 AI Startups - 25+ AI products/features: AI SaaS, chatbots, agents, copilots, OpenAI / Claude integrations. 💰 FinTech - 3+ projects: Stripe Connect, billing, payment flows, invoicing. 🎮 Gaming - 5+ projects, including 2 major global gaming brands: dashboards, analytics, real-time interactions. 📚 EdTech - 5+ projects: student dashboards, progress tracking, content platforms. 📣 MarTech - 1 global market-leading project: dashboards, analytics, segmentation, workflows. ⚽ SportsTech - 10+ projects: live data, dashboards, events, rankings, stats, mobile apps. 📌 How We Work 1️⃣ Discovery & technical planning 2️⃣ Engineer matching within 24h 3️⃣ 2-week trial period 4️⃣ Weekly demos and reports 5️⃣ CTO-approved delivery with code review and QA 6️⃣ Long-term support after launch 🚀 Building a SaaS, MVP, marketplace, React app, Next.js platform, React Native app, AI product, or mixed-stack web/mobile platform? Click “Invite” or “Hire” - I’ll help you clear the estimate or discovery phase within 24 hours or less.

I help startups and growing businesses design, build, and scale 🚀 SaaS products, 🏪 marketplaces, 🛒 ecommerce platforms, 📱 mobile applications, and 💳 subscription-based businesses. With 10+ years of experience as a 💻 Full Stack Developer, 🏗️ Solution Architect, and 👨‍💼 Technical Lead, I deliver scalable products from MVP to production. My expertise covers SaaS development, marketplace platforms, subscription billing systems, payment infrastructure, API integrations, cloud-based applications, and business-critical payment flows. I don't just implement features — I help companies make technical decisions, define architecture, optimize billing processes, integrate payment systems, and launch products faster. ⚡ 🎯 Core Expertise ✅ Full Stack Development • ✅ SaaS Development • ✅ Marketplace Development • ✅ Ecommerce Development • ✅ Subscription Platforms • ✅ Subscription Billing • ✅ Payment Gateway Integration • ✅ Stripe Integration • ✅ PayPal Integration • ✅ Checkout Development • ✅ API Integration • ✅ Mobile App Development • ✅ React Development • ✅ Flutter Development • ✅ Firebase Development • ✅ Supabase Development • ✅ Technical Product Ownership • ✅ Solution Architecture 💳 Payment & Billing Expertise I specialize in building and optimizing payment systems for SaaS businesses, marketplaces, ecommerce stores, and mobile applications. 💰 Stripe Checkout • Stripe Elements • Stripe Payment Element • Stripe Billing • Stripe Subscriptions • Stripe Connect • Stripe Webhooks • Stripe Customer Portal • Stripe Payment Intents • Stripe Setup Intents • Stripe Invoicing • Stripe Tax • Stripe Payment Links • Stripe Radar • Stripe Identity • Stripe Connect Marketplace • Stripe Connect Payouts • Stripe Webhook Development • Stripe Webhook Troubleshooting • Stripe API Integration • Stripe Billing Automation • Stripe Subscription Management • Stripe Subscription Lifecycle Management • Stripe Checkout Optimization • Stripe Checkout Customization • Stripe Recurring Billing • Stripe SaaS Billing • Stripe Marketplace Payments • Stripe Vendor Payouts • Stripe Multi-Currency Payments • Stripe Upgrade & Downgrade Flows • Stripe Trial Management • Stripe Revenue Optimization • Stripe Fraud Prevention • Stripe Payment Security • Stripe Migration 💸 PayPal Integration • PayPal Checkout • PayPal API Integration • PayPal Subscriptions • PayPal Recurring Payments • PayPal Webhooks • PayPal Billing Agreements • PayPal Marketplace Payments 🔗 Payment Gateway Integration • Subscription Billing • Recurring Payments • Billing Automation • Customer Portal • Upgrade & Downgrade Flows • Trial Management • Multi-Currency Payments • Vendor Payouts • Marketplace Payments • Refund Automation • Payment Infrastructure 🚀 SaaS & Product Development I have extensive experience building SaaS platforms and subscription-based products. ☁️ SaaS MVP Development • SaaS Architecture • Multi-Tenant SaaS Applications • B2B SaaS Platforms • B2C SaaS Platforms • AI SaaS Products • SaaS Billing Systems • SaaS Payment Infrastructure • SaaS Subscription Management • SaaS Analytics & Reporting • SaaS Integrations • SaaS Scaling & Performance Optimization • SaaS Checkout Optimization • SaaS Revenue Optimization • Mobile SaaS Applications • SaaS Marketplace Platforms 🏪 Marketplace Expertise I help businesses build and scale marketplace platforms with automated payments and vendor management. 💳 Stripe Connect • Marketplace Payments • Vendor Payouts • Commission Systems • Multi-Vendor Platforms • Booking Platforms • Service Marketplaces • Product Marketplaces • Creator Platforms • Marketplace Billing Systems • Marketplace Checkout Flows • Marketplace Revenue Models 🧠 Technical Product Ownership I often work as a technical partner helping founders and business owners turn ideas into scalable products. 🏗️ Technical Product Ownership • Product Architecture Design • MVP Planning & Development • Startup Product Development • Technical Leadership • Solution Architecture • System Design • Product Roadmap Execution • Platform Scaling • Development Team Leadership • Business Requirements Analysis • Third-Party Integrations • Payment Infrastructure Design • SaaS Architecture Consulting 🛠️ Technologies Backend: PHP • Laravel • MySQL • Redis • Elasticsearch • Apache Solr Frontend: JavaScript • React • Vue.js Mobile: Flutter Backend as a Service: Firebase • Supabase Cloud & Infrastructure: AWS • S3 • CloudFront • Lambda • Docker 📈 Recent Project Experience 🚀 SaaS Billing & Subscription Platforms: Subscription Billing • Stripe Billing • Stripe Subscriptions • Checkout Optimization • Payment Gateway Integration • Recurring Billing • Subscription Lifecycle Management • Revenue Optimization 🏪 Marketplace Solutions: Stripe Connect • Marketplace Payments • Vendor Payouts • Commission Systems • Payment Infrastructure • Multi-Vendor Platforms 🛒 Ecommerce Platforms: Shopify Integrations • WooCommerce Integrations • Stripe Payments • PayPal Payments

🎯 I build apps that hold up when real users, real payments, and real traffic hit them. 🎯 12 years in software engineering, 9 years specialized in Bubble io, 150+ shipped projects — SaaS platforms, AI-powered apps, marketplaces, CRMs, and MVPs that made it past launch day, with 80% going on to raise investment. ⚒️ HOW I BUILD ✔️150+ products as a Bubble Full Stack Developer, Bubble Developer: Bubble, JavaScript, Java, PHP, Angular, MySQL, Responsive Design, custom plugin development. ✔️60+ AI systems as a Bubble AI Developer, No Code AI Developer: OpenAI GPT, Anthropic Claude, Gemini, RAG pipelines, AI agents, bubble ChatGPT integrations. ✔️40+ automation ecosystems as a Bubble Automation Developer, No Code Automation Engineer: n8n, Zapier, Make, Airtable, Zoho, Twilio, Stripe, Meta APIs — supporting $4M+ in client transaction volume. ✔️Engineering foundation: CS degree, Master's in Software Engineering, magento developer-level backend thinking applied as a Bubble No Code Developer. 🚚 WHERE I DELIVER ✔️As a Bubble Developer, Bubble io Developer — 150+ builds spanning Bubble MVP, Bubble SaaS Build, Bubble Marketplace, Bubble CRM Build, and Bubble Social Network projects generating $6M+ in combined client revenue. ✔️As a Bubble Full Stack Developer, No Code Full Stack Developer — database architecture, and workflow design inside Bubble, reducing dev costs by 30–50% vs. traditional stacks. ✔️As a Bubble MVP Developer, Investment-Ready MVP Builder — 80% of MVPs shipped went on to raise pre-seed or seed funding. ✔️As a Bubble AI Developer, AI Integration Developer — GPT, Claude, and Gemini integrations powering chatbots, RAG search, and AI agents inside live Bubble apps, lifting user retention by 22–30%. ✔️As a Bubble API Developer, No Code Integration Specialist — Stripe, Twilio, Meta, and custom third-party systems processing $4M+ in transactions across client platforms. ✔️As a Bubble Automation Developer, Workflow Automation Engineer — n8n, Zapier, and Make stacks handling lead capture, CRM routing, and internal ops automation, worth an estimated $500K+ in recovered labor cost. ✔️As an AI-Enhanced No Code Developer, Bubble Prototype Developer — using Lovable and modern AI tooling to accelerate Bubble development cycles by 40%, shortening time-to-revenue for clients. 🔥 ACHIEVEMENTS ✔️12 years as a software engineer, 9+ years as a Bubble Developer, Bubble io Developer, No Code Full Stack Developer, 150+ applications shipped from prototype to production. ✔️80% of MVPs built went on to raise investment — pre-seed to Series A — as a Bubble MVP Developer, Startup Bubble Developer trusted for fundable, demo-ready builds. ✔️$6.2M+ in client-side business impact, $1.4M+ direct project revenue, €780K paid MVP contracts, £18M annual business volume touched as a Bubble Full Stack Developer. ✔️30,000+ active users across bubble io web applications where backend architecture and API integrations cut load times by 35%+ as a Bubble Developer. ✔️60+ AI-powered Bubble apps built with OpenAI GPT, Anthropic Claude, and Gemini integrations as a Bubble AI Developer — chatbots, RAG pipelines, and autonomous AI agents driving $900K+ in automation-linked savings. ✔️40+ automation stacks delivered with n8n, Zapier, Make, Airtable, Zoho, and Twilio as a No Code Automation Developer, cutting manual workflow time by 50–75% and saving clients an estimated 12,000+ operational hours. ✔️35+ Bubble io SaaS Build and Bubble io Marketplace launches with Stripe and Meta API integrations, processing $4M+ in platform transaction volume as a Bubble No Code Developer, Bubble SaaS Developer. ✔️3–5 week average MVP to working prototype turnaround, 40% faster than industry standard, as a Bubble Prototype Developer, No Code Engineer. ✔️CS degree + Master's in Software Engineering — technical depth in JavaScript, Java, PHP, Angular, MySQL backing every build as a Bubble Full Stack Developer. ✔️99%+ delivery consistency across 25+ international clients in the US, UK, and Europe as a Bubble io Full Stack Developer, No Code Developer. 🏆 INDUSTRY IMPACT Startup MVPs, Fundable Prototypes, Pre-Seed to Series A builds — 80% investment-raise rate as a Bubble MVP Developer, Investor-Ready Bubble Developer. SaaS Platform, Internal Tools, Bubble io SaaS Build — 30,000+ users, $2.1M+ in ARR supported, 35%+ faster load times as a Bubble Full Stack Developer, SaaS Bubble Developer. B2B Marketplace, Bubble io Marketplace, Two-Sided Marketplace — thousands of listings, $4M+ GMV processed, 25%+ better lead-to-conversion as a Bubble Marketplace Developer, No Code Developer. AI-Powered Platforms, AI Agent Systems, RAG Chatbots — 60+ products, $900K+ in automation-driven cost savings as a Bubble AI Developer combining OpenAI, Claude, and Bubble backend logic. CRM Systems, Bubble io CRM Build, Workflow Automation — 50–75% less manual admin work, 12,000+ hours saved annually as a Bubble Automation Developer through n8n and Zapier automation.

I'm a full stack developer. Been building web apps for about 8 years now — for startups, agencies, and directly with business owners. I've shipped ecommerce sites, internal dashboards, custom tools, and a bunch of WordPress projects. Things that actually get used. Here's the tech I work with regularly: ✔ Backend: Node.js, PHP, Python, Go, .NET Core, Java Spring Boot, Ruby on Rails ✔ Frontend: React, Next.js, Vue, Nuxt, Angular, TypeScript, Tailwind, Svelte, Alpine.js ✔ Ecommerce & CMS: Shopify, WooCommerce, Medusa, BigCommerce, Magento, Stripe, Snipcart, WordPress, Sanity, Strapi, Payload CMS ✔ Database: PostgreSQL, MySQL, MongoDB, Firebase, Supabase, DynamoDB, Elasticsearch, Redis, Prisma, Drizzle ✔ DevOps & Cloud: AWS (EC2, Lambda, RDS, S3), Vercel, Netlify, Render, Heroku, DigitalOcean, Docker, Kubernetes, CI/CD, GitHub Actions, Cloudflare ✔ API & Integration: REST, GraphQL, tRPC, Webhooks, Apollo, Hasura, Express, FastAPI, Laravel, NestJS ✔ Tools: Git, GitHub, GitLab, Bitbucket, Jira, Linear, Asana, Slack, Notion, Postman, Sentry, Agile, Scrum, Kanban How I work: - I write clean, readable code. Nothing fancy. - I communicate clearly. Daily updates, no surprises. - I finish what I start. No dropped projects. - I care about performance. Slow sites lose customers. - I read specs carefully. Then build what you actually need. I keep up with new tech, but I don't chase trends. I pick what fits your project and budget. Got something in mind? Let's talk.

🚀 𝐀𝐧𝐲𝐨𝐧𝐞 𝐜𝐚𝐧 𝐛𝐮𝐢𝐥𝐝 𝐚𝐧 𝐌𝐕𝐏. 𝐁𝐮𝐭 𝐧𝐨𝐭 𝐞𝐯𝐞𝐫𝐲𝐨𝐧𝐞 𝐜𝐚𝐧 𝐭𝐮𝐫𝐧 𝐢𝐭 𝐢𝐧𝐭𝐨 𝐚 𝐬𝐜𝐚𝐥𝐚𝐛𝐥𝐞 𝐒𝐚𝐚𝐒 𝐛𝐮𝐬𝐢𝐧𝐞𝐬𝐬. 🔥 85+ completed projects (40+ SaaS & MVP platforms) 💰 Startup MVP generated $500K+ revenue in its first 6 months 👥 SaaS products supporting 10K–50K active users 📈 One platform grew from 2K to 7K users through continuous product improvements ⚡ Backend systems processing 300K–500K API requests every month 🚀 Startup MVPs delivered in 2–4 weeks 📊 5+ years building SaaS platforms & Startup MVPs 📦 100+ API integrations completed across production systems ⚙️ 20+ backend architectures designed from scratch 🧠 AI integrations across 30+ commercial projects I help founders build SaaS platforms, Startup MVPs, AI-powered applications, Internal Business Systems, Customer Portals, Marketplace Platforms, and scalable Web Applications using React, Next.js, Node.js, Supabase, PostgreSQL, Stripe, Redis, and modern AI APIs. As a SaaS Developer, MVP Developer, Full Stack Developer, Software Developer, and Web Developer, I've delivered 85+ production projects, including 40+ SaaS & MVP platforms, helping startups validate ideas faster, launch products in 2–4 weeks, and scale applications supporting 10K–50K active users. Many companies hire me as a SaaS Developer, MVP Developer, Full Stack Developer, Startup Developer, and AI SaaS Developer because I don't just build software—I build products designed to scale. Systems I've developed process 300K–500K API requests monthly, integrate 100+ third-party APIs, and continue growing years after their initial MVP launch. Unlike many Software Developers, I focus on the entire product lifecycle—from idea validation and MVP planning to production infrastructure, subscription systems, customer portals, internal business tools, and long-term SaaS scalability. 🏆 Why Founders Hire Me as a SaaS Developer 5+ years working as a SaaS Developer, MVP Developer, and Full Stack Developer 85+ completed projects, including 40+ SaaS & MVP platforms Startup MVP delivered in 2–4 weeks without sacrificing scalability Products supporting 10K–50K active users after launch One Startup MVP generated $500K+ revenue during its first 6 months One SaaS platform grew from 2K to 7K users through continuous feature releases Backend systems processing 300K–500K API requests every month 100+ API integrations, including Stripe, Supabase, OpenAI, logistics providers, CRMs, authentication services, and payment gateways Redis optimization reducing database load by 70%+ on high-traffic SaaS platforms React performance optimization improving Lighthouse scores to 90+ and reducing frontend bundle sizes by 40%+ Experience building subscription platforms, customer portals, internal business systems, marketplace platforms, admin dashboards, and multi-tenant SaaS applications Production-ready architecture designed to support years of product growth instead of temporary MVP prototypes 🚀 Startup Growth As a SaaS Developer, MVP Developer, Startup Developer, and Full Stack Developer, I help founders move from idea to production-ready software in 2–4 weeks. Over the last 5+ years, I've worked with 40+ SaaS & MVP products, helping startups validate ideas faster, launch earlier, and build scalable software capable of supporting 10K–50K users without rebuilding the entire platform. 🚀 Production-Ready Software As a Software Developer, Web Developer, and SaaS Developer, I don't build throwaway prototypes. I build production-ready SaaS applications with scalable architecture, authentication, subscription systems, customer portals, analytics dashboards, and internal business systems. Several platforms I've built now process 300K–500K API requests every month, while continuously shipping new features years after their initial MVP launch. 🚀 API & Integration Experience As a Full Stack Developer, SaaS Developer, and Backend Developer, I've completed 100+ API integrations across payment systems, logistics providers, AI platforms, authentication services, CRMs, analytics platforms, and third-party business software. My experience includes Stripe, Supabase, OpenAI, REST APIs, WebSockets, PostgreSQL, Redis, and scalable backend services powering modern SaaS products. 🚀 Performance & Scalability As a SaaS Developer and Software Developer, performance is always part of the architecture. Across multiple production applications, I've reduced database load by 70%+, improved Lighthouse scores to 90+, optimized React applications by reducing bundle sizes by 40%+, and built backend services capable of supporting hundreds of thousands of monthly requests while maintaining long-term scalability. Beyond my work as a SaaS Developer and MVP Developer, I've completed 85+ projects as a Web Developer, React Developer, and Mobile App Developer, building production-ready web applications, SaaS platforms, customer portals, dashboards, and cross-platform mobile apps supporting 10K–50K users.