Serhii K.

Complex under the hood. Simple where it matters. I’m a Full-Stack Developer who turns ambitious ideas into reliable digital products — SaaS platforms, AI-powered applications, e-commerce solutions, and custom web platforms. I handle the entire journey: from architecture and backend engineering to frontend development, API integrations, AI implementation, and deployment. My philosophy? Technology should solve problems, not create new ones. WHY CLIENTS CHOOSE ME I focus on building software that works reliably in real business environments. My approach includes understanding the business requirements, choosing the right architecture, developing the core functionality, integrating APIs and external services, handling errors and edge cases, and preparing the application for deployment and future development. • 100% Job Success • Top Rated Plus on Upwork • 5-star client feedback FULL-STACK DEVELOPMENT As a Full-Stack Developer, I build complete web applications from frontend to backend, ensuring that the user interface, business logic, databases, APIs, and external services work together. • Custom web application development • SaaS platform development • Frontend development with React and Next.js • Backend development with Python, FastAPI, Django, and Node.js • Database design and integration • Authentication and role-based access control • Third-party API integration • Real-time features and asynchronous processing BACKEND DEVELOPMENT & API INTEGRATION As a Backend Developer, I design, develop, and maintain scalable backend systems that power web applications, SaaS platforms, AI applications, and automated business workflows. I build server-side architecture, business logic, databases, and APIs that connect frontend applications, AI models, and third-party services. • Python backend development • FastAPI and Django development • Node.js backend development • REST API development • GraphQL API integration • Database architecture and optimization • Microservices and backend automation • Docker and cloud deployment AI AUTOMATION & BUSINESS PROCESS AUTOMATION & AI INTEGRATION As an AI Automation Developer, I design and build intelligent automation systems that connect AI models, business applications, APIs, databases, and internal workflows. I help businesses automate repetitive tasks, streamline operations, eliminate manual data processing, and integrate AI into existing products and business processes. • AI workflow automation • Business process automation • AI agent workflows • Lead generation and qualification • CRM and email automation • Document processing automation • Automated data extraction and enrichment • Automated reporting and notifications • Scheduled tasks and background processing • n8n, Make, and Zapier integrations • AI-powered SaaS workflows SAAS PLATFORMS & CUSTOM SOFTWARE As a SaaS Developer, I design, develop, and scale custom SaaS applications, subscription-based platforms, and business software from initial concept to production deployment. I handle the full SaaS development lifecycle, including technical architecture, frontend and backend development, database design, API integrations, authentication, billing workflows, testing, deployment, and ongoing optimization. • SaaS application development • Custom business platforms • AI-powered SaaS products • Backend architecture and API development • Subscription-based application functionality • Database-driven web applications • Third-party service integrations • Admin panels and analytics dashboards • Workflow and process management systems • Internal business applications • MVP development and product prototyping • Existing application improvements and integrations Whether you need a new product built from scratch or an existing application enhanced with AI, automation, APIs, or data processing, I can work across the technical components required to deliver the solution. TECHNOLOGY STACK Languages: Python, JavaScript, TypeScript, SQL Backend: FastAPI, Django, Flask, Node.js Frontend: React, Next.js AI & LLMs: OpenAI API, GPT, Claude, Gemini, LangChain, LangGraph, RAG, AI agents Automation: n8n, Make, Zapier, Python automation, Webhooks Data Engineering: Pandas, ETL/ELT, data extraction, data transformation, data pipelines Databases: PostgreSQL, MongoDB, Redis, vector databases APIs & Architecture: REST APIs, GraphQL, microservices, third-party integrations Infrastructure: Docker, AWS, GCP, background workers, cloud deployment If you need a Full-Stack Developer, Python Developer, Backend Developer, AI Developer, AI Integration Developer, Automation Developer, or Data Engineer, send me your project requirements. I can help you design, build, integrate, and scale the right solution.