Serhii Kalyna
Senior Full-Stack Developer & Web Team Lead
18+ years building web applications. Based in Kyiv, Ukraine.
Currently focused on AI development, LLM integrations, and making that knowledge accessible for developers.
My Story
I started writing code in 2007 — not because I studied computer science, but because I couldn’t stop. My formal education was in metallurgy and pharmacy, neither of which I completed. What I did complete was roughly 18 years of building real-world web applications, debugging production systems at 2am, and leading teams through rewrites, migrations, and launches.
I didn’t follow the traditional path into tech. I learned by building — small projects, then bigger ones, then projects with real users depending on them. That’s still how I work.
What I Do
I’m a Web Development Team Lead at FireBit LTD, where I oversee full-stack development across multiple products. My day-to-day spans architecture decisions, code reviews, mentoring developers, and hands-on engineering when the problem is interesting enough.
On the side, I run kalyna.pro — this blog. I started it to document what I’m learning about AI and LLM integrations. Writing about something forces you to actually understand it.
Tech Stack
My core stack has evolved over 18 years, but the constants are:
Lately I’ve been spending most of my learning time on: Python, the Anthropic Claude API, LangChain, vector databases (ChromaDB, Pinecone), and building AI agents. That’s what you’ll find most of on this blog.
This Blog
kalyna.pro is an AI Dev blog aimed at working developers — people who already know how to code and want to understand how to work with LLMs effectively.
I write about:
- Claude API and Anthropic’s ecosystem — practical tutorials, not marketing
- Building AI agents and multi-agent pipelines in Python
- RAG (Retrieval-Augmented Generation) — real implementations, not toy examples
- Tools I actually use: Cursor AI, n8n, LangChain, vector databases
- Cost optimization and production patterns for LLM applications
Everything is based on actual usage. If it’s on this blog, I’ve built it.
Contact
Best way to reach me: [email protected]
I’m open to consulting on AI integrations, code reviews, and architecture questions for teams adding LLMs to their stack.