Denis Klymenko | AI Agent Architect & Full-Stack Product Engineer

About Me

Lead AI Architect & Senior Product Engineer. I don't just “plug in” OpenAI APIs — I build predictable AI systems where LLM reasoning is governed by rigid business logic.

Key Achievements

◆Enterprise AI Agent for love💗epil (18 studios, 5 countries). Brain-First architecture with 21 orchestrated tools, fine-tuned GPT-4.1 Mini, LLM observability via Langfuse OpenTelemetry, multi-channel deployment (Web, Telegram, Instagram, Facebook). Solo-delivered.
◆20 projects delivered (14 from scratch). Engineered a scalable distributed SaaS ecosystem serving 5 countries with Domain-Driven Design, Stripe payments, and GDPR compliance.
◆Full-Cycle Development: E2E ownership — architecture, AI agent design, FE/BE integration, testing (Vitest), CI/CD, deployment to Vercel.

Value I bring:

→Brain-first AI systems — rigid business logic governs LLM reasoning, not prompt tricks
→Tool Orchestration (21 tools), Fine-Tuning pipelines, Prompt Engineering for production AI agents
→LLM observability: Langfuse + OpenTelemetry traces every tool call, token usage, cost per conversation
→Architecting for scale: multi-domain, multi-currency, i18n-ready systems with unified data modeling

Recent Highlights

✦Enterprise AI Agent with 21 orchestrated tools, FSM booking sessions, and support incident tracking
✦Fine-tuned GPT-4.1 Mini with custom data pipeline (merge, validate, audit, quality-check)
✦pgvector semantic search with OpenAI text-embedding-3-small (FAQ, services, studios, cities, abonnements)
✦Distributed service architecture: AI Orchestrator, Analytics Engine, Core API, Headless CMS, and Admin Dashboard

Core Competencies

AI Agent Architecture (Brain-First, 21 tools, FSM)OpenAI API, Vercel AI SDK, Langfuse, pgvectorFine-Tuning, Prompt Engineering, Tool OrchestrationFull-Stack: Next.js 16, React 19, TypeScript, Node.jsPrisma (Complex Data Modeling), PostgreSQL, Stripe, NextAuthMulti-domain i18n (6 lang, 4 currencies, GDPR)Strapi CMS, Resend, React Email, DeepLVitest, ESLint, Husky, TypeScript strictVercel, AWS, Firebase, Telegram Bot API

Skills

Technologies and tools I use to build scalable, high-performance applications.

AI & LLM

OpenAI

Vercel AI SDK

Langfuse

pgvector

Anthropic

LangChain

Frontend

TypeScript

React 19

Next.js 16

Zustand

React Hook Form

Framer Motion

i18next

TanStack Query

Backend & Data

Node.js

PostgreSQL

Prisma

Stripe

Resend

NextAuth

Strapi CMS

Zod

UI & Design

Material UI

Tailwind CSS

SASS

React Email

Cloud & DevOps

Vercel

AWS

Git

Firebase

Telegram Bot API

Analytics & SEO

Vercel Analytics

Google Analytics

Microsoft Clarity

Google Maps API

Testing & Quality

Vitest

ESLint

Husky

Featured Projects

Brain-first AI Agents, Agentic Workflows, and scalable multi-domain SaaS architectures.

Enterprise AI Agent for love💗epil

Lead AI Architect2025 - Present

Brain-First architecture AI Agent for European beauty chain (18 studios, 5 countries). Solo-delivered.

My Contributions

•Brain-First architecture with 21 orchestrated tools — booking, cart, services, studios, knowledge base, availability, handoff
•Fine-tuned GPT-4.1 Mini with custom training data pipeline (merge, validate, audit, quality-check scripts)
•LLM observability via Langfuse OpenTelemetry — traces every tool call, token usage, cost per conversation
•pgvector semantic search with OpenAI text-embedding-3-small for FAQ, services, studios, cities, abonnements
•Multi-channel deployment: website widget, Telegram Bot API, admin panel with incident review
•Stateful booking sessions with funnel analytics (outcome tracking, drop-off analysis)
•Support incident system — auto-captures conversation snapshots on handoff, dislike, or complaint

Client Results

✓Live in production across 18 studios in 5 countries
✓Near-zero hallucination rate via brain-first control flow
✓4 channels: Website, Telegram, Instagram, Facebook

Technologies

OpenAI GPT-4.1 MiniVercel AI SDKLangfusepgvectorNext.js 16PrismaPostgreSQLTelegram Bot APIVitest

Read Case Study

love💗epil Multi-domain SaaS Ecosystem

Senior Product Engineer E2E2024 - Present

Comprehensively architected distributed ecosystem powering a European beauty chain — decoupling frontend, admin, analytics, AI service, and CMS.

My Contributions

•Architected multi-domain i18n system (5 countries, 6 domains, 6 languages, 4 currencies, GDPR-compliant)
•Built custom analytics platform with cross-domain session stitching, multi-touch attribution, and Vercel Drains
•Full admin panel with RBAC, Stripe payments, loyalty programs, booking management, FAQ editor, and content translations via DeepL
•Enterprise-grade Prisma data layer implementing Domain-Driven Design (DDD) across Studio Management, Booking Engine, Loyalty Logic, and Content Delivery
•Transactional email system with React Email + Resend, i18n-aware templates
•Strapi CMS with auto-translation, drag-drop content types, REST cache plugin
•Core Web Vitals optimization: LCP < 2.5s, INP < 200ms, 96% Real User Experience Score

Client Results

✓30K+ monthly active users across 6 European domains
✓96% Real User Experience Score (mobile)
✓End-to-End Architecture Ownership

Technologies

Next.js 16React 19TypeScriptPrismaPostgreSQLStripeNextAuthStrapiResendReact EmailVercelGoogle Maps APIFirebaseMicrosoft ClarityZustandTanStack QueryZodi18nextDeepL

Career Timeline

Corva

Senior Frontend Developer

December 2025 - Present

Stack

ReactTypeScriptReduxHighchartsStyled ComponentsJestReact Testing Library

Responsibilities

Focusing on performance optimization and platform stability for mission-critical drilling analytics. Refactoring complex React components to improve rendering efficiency and maintainability. Delivering robust feature enhancements and ensuring long-term code health.

Achievements

Optimized core visualization components, reducing render time for large datasets. Streamlined maintenance workflows for legacy modules.

love💗epil

AI Architect | Senior Product Engineer

August 2024 - Present

Stack

Next.js 16React 19TypeScriptPrismaPostgreSQLOpenAI APIVercel AI SDKLangfuseStripeMUIDeepLVercel Drains

Responsibilities

Led end-to-end development of a high-traffic ecosystem serving 5 countries (6 domains, 6 languages, 4 currencies) with 30K+ MAU. Orchestrated the full lifecycle of AI, Analytics, and Infrastructure products.

Achievements

Achieved 96% Mobile Performance Score (LCP < 2.5s, INP < 200ms). Implemented dynamic hreflang, JSON-LD, and multi-region sitemaps for SEO dominance.

Projects

AI Booking Agent (LoveGPT)

Brain-First architecture: fine-tuned GPT-4.1 Mini orchestrates 20+ tools. Features Custom State Guard (Pending Question pattern) for context retention and "askUser" pattern for controlled flows. Fully observable via Langfuse + OpenTelemetry. Semantic search via pgvector.

Analytics & Attribution Platform

Custom platform unifying user journeys across 6 TLDs via cross-domain session stitching. Engineered phone-based attribution matching CRM bookings to traffic sources (Google/Meta). Real-time event ingestion via Vercel Drains (1000+ events/batch) with AI-powered insights.

Admin & Infrastructure

DeepL-powered 6-language auto-localization engine. Granular RBAC system, Stripe billing integration, and real-time CRM synchronization.

Blackbird Lab

Senior Fullstack Engineer

March 2021 - Present

Stack

TypeScriptReact 19Next.js 15ZustandReduxRedux-SagaRESTGraphQLMUIAnt DesignTailwind CSSPrismaPostgreSQLJestReact Testing LibraryGoogle AnalyticsVercel

Responsibilities

Led the modernization of the company's frontend infrastructure, transitioning from legacy stacks to a unified Next.js architecture. Championed a "Security-First" engineering culture by integrating automated vulnerability constraints directly into the CI/CD pipeline and architectural patterns.

Achievements

Secured sensitive data flows across 3 internal products by re-engineering the authentication and session management layer. Successfully migrated 50K+ lines of code to TypeScript/Next.js, reducing technical debt and improving developer velocity.

S-PRO

Middle Frontend Developer

March 2020 - March 2021

Stack

ReactReduxRedux-SagaReact Router v4FormikSCSSAnt DesignFlexbox GridLodashMoment.jsNivo RocksESLint (Airbnb)

Responsibilities

Building robust frontend solutions and developing new features from requirements. ensuring best practices through code refactoring and unit testing. Collaborating on project estimation and workload assessment.

Achievements

Delivered 2 greenfield projects from scratch, including a complex energy storage analytics platform.

Projects

Modo Energy

Analytics platform for energy storage assets in the UK market.

Zymergen

DNA science data visualization and management tool for a major US biotechnology company.

Noosyntech

November 2018 - March 2020

Stack

ReactReduxRedux-SagaRedux-FormSASSANTDFlexBox GridLodashMomentReactDnD

Responsibilities

Built dynamic UI components, optimized rendering performance, and implemented unit tests for critical flows.

Projects

Frood

Large-scale marketplace platform connecting buyers and sellers in the Asian market.

7eminar

November 2017 - November 2018

Stack

JavaScript (jQuery)HTML/PugSASSLaravelJSON

Responsibilities

Migrated the main platform to a responsive modular architecture (Bootstrap 3). Implemented dynamic UI interactions and complex email template systems.

Achievements

Created and optimized over 80 high-conversion landing pages and responsive email templates.

Other Information

Education

National Academy Security Service of Ukraine, specialty – Administration of Restricted Information Security.

English

Upper Intermediate

Design Paterns

DRY, KISS, YAGNI, SOLID, SINGLETONE