Oleksandr S.

🏆 AI Full-Stack Developer | $200K+ Earned · 100% JSS I build and scale AI-powered SaaS, B2B and FinTech products using Next.js, React, JavaScript, TypeScript, Node.js and Python. I can take ownership from architecture and Full-Stack Development through AI Integration, API Integration, payments, data workflows, testing and production deployment. My core stack is Next.js, React, TypeScript, Node.js, Python, FastAPI, Supabase and PostgreSQL, with OpenAI API and Claude / Anthropic for AI Agents, RAG, LLM APIs and LLM-powered product features. PROBLEMS I SOLVE ❌ An AI or SaaS MVP / V1 works in a demo but isn't ready for real users or production deployment. ❌ A SaaS product needs AI Agents, RAG or LLM Integration integrated into existing workflows. ❌ An existing platform is becoming slow, difficult to maintain or expensive to extend and needs debugging or performance optimization. ❌ There is no clear software, system or database architecture for moving from MVP to a scalable SaaS product. ❌ A FinTech or data-heavy product needs reliable APIs, payments, Stripe, webhooks, integrations and infrastructure. ❌ A B2B platform needs dashboards, subscriptions, authentication, authorization, RBAC / role-based access or complex business logic. I approach these as product engineering problems, not isolated development tasks. Architecture, data models, REST APIs, AI infrastructure, security, privacy and deployment decisions are made with the next stage of the product in mind. 150+ shipped projects. 20+ countries. Zero rebuilds requested. ──────────────────────────────────────── WHAT I BUILD 🔷 AI SaaS & B2B Products SaaS MVPs and production Web Applications using Next.js, React, TypeScript, Node.js, Python, FastAPI, Supabase and PostgreSQL. Authentication, subscriptions, payments, dashboards, admin systems, REST APIs, GraphQL and third-party API Integration. 🔷 AI Agents, RAG & LLM Features AI Agents, AI Agent Development, agentic workflows, RAG, semantic search, vector databases, function/tool calling and LLM-powered features using OpenAI, OpenAI API, Claude, Anthropic, LangChain and LangGraph. I integrate AI into the actual product workflow rather than building a disconnected chatbot. I also work with AI-assisted development using Claude Code and Cursor. 🔷 FinTech & Data-Heavy Platforms Financial SaaS, FinTech, analytics platforms and products with complex data flows. Experience includes payment integrations, Payment Gateway Integration, Stripe, subscriptions, webhooks, reconciliation, payouts, KYC / KYB, identity verification, role-based access, dashboards, reporting and backend architecture built around reliability and maintainability. 🔷 Full-Stack Product Development Frontend and backend development with Next.js, React, Node.js, TypeScript, JavaScript, Python, FastAPI and NestJS. I can build a product from scratch or step into an existing production codebase to improve architecture, scalability, debugging, performance and maintainability. This includes Internal Tools, Booking / Scheduling, ERP, CRM integrations and E-Commerce functionality. 🔷 Integrations & Production Infrastructure Stripe, OpenAI, Claude, MCP, third-party APIs, Supabase, PostgreSQL, MongoDB, AWS, GCP, Vercel, Docker and CI/CD. I build the surrounding infrastructure so product, AI, payments and external systems work together reliably, including monitoring, observability, logging, audit logs and secure applications. ──────────────────────────────────────── HOW I WORK Architecture before code: clear decisions around stack, data, APIs, database architecture and infrastructure. Production over demos: built for real users, data and workflows with testing, QA, UAT, security and production readiness in mind. Iterative delivery: working product increments instead of a long black-box development cycle. Existing products welcome: I don't push unnecessary rebuilds when the current architecture can be improved. Built to scale and hand off: maintainable code and architecture another engineer can continue working with. ──────────────────────────────────────── Behind this profile is SDA, the software development company I founded. I stay directly involved in architecture and engineering while having additional design and development capacity available when a product needs it. 💡 Building an AI SaaS product, scaling an existing B2B platform or developing a FinTech product? Send me the details and I'll take a look. Technology: Next.js, React, JavaScript, TypeScript, Node.js, Python, FastAPI, NestJS, Supabase, PostgreSQL, MongoDB, OpenAI API, Claude API, AI Agents, RAG, LangChain, LangGraph, MCP, Vector Databases, API Integration, API Development, REST API, GraphQL, Webhooks, Stripe, Payment Systems, RBAC, Database Architecture, AWS, GCP, Vercel, Docker, CI/CD, React Native, Mobile App Development, Android, iOS, Tailwind CSS, HTML5, CSS3, PHP, WordPress.