Tech Stack
Tools I reach for when building production systems.
Backend
FastAPI Django Flask gRPC WebSockets Mobile Backend (iOS / Android) Concurrency (asyncio)
Patterns & Practices
DDD TDD SOLID / Clean Architecture Microservices Event-Driven Architecture CQRS Circuit Breaker / SAGA
AI / LLM
LLM APIs (OpenAI / Anthropic / Gemini) LangChain RAG Vector Search Embeddings (Text / Image) Fine-tuning (LoRA/QLoRA) Audio Pipeline (Whisper / TTS / Voice Cloning) Hugging Face PyTorch Transformers (T5/BERT) / Time Series Forecasting Custom CUDA Kernels MCP Servers
ML / Data
Recommendation Systems NumPy / Pandas
Data & MQ
PostgreSQL Redis MongoDB Memgraph InfluxDB Kafka RabbitMQ Celery Elasticsearch CouchDB Solr
Infrastructure
AWS (ECS, S3, SQS, Lambda, RDS, ElastiCache, CloudWatch) Docker Kubernetes Helm Terraform Ansible GCP GitLab CI/CD OpenTelemetry
Integrations
Payment Gateways (Stripe, LiqPay, +more) Twilio Firebase Auth Social Media APIs OpenStreetMaps Push Notifications Web Scraping (Playwright / Anti-detection / Proxies)
Monitoring & Testing
Sentry Grafana Prometheus Pytest Locust
Hardware & IoT
TCP Servers IoT Protocols
Experience
10+ years building systems that handle real load and real money — and ready to do it for your team.
Backend Engineer
NDA · Israel
- → Video recommendation system: +75% user engagement
- → Monolith-to-microservices migration on AWS (ECS, gRPC)
- → Integration testing strategy: 70% coverage, -40% critical bugs in production
AWS (ECS, S3, SQS, Lambda, CloudWatch)gRPCPostgreSQLMongoDBDockerRecommendation SystemsCollaborative Filtering
Senior Python Developer
Zakaz.ua · Kyiv
- → Django → FastAPI migration, API performance boost
- → LLM-based product preprocessing: -25% manual processing costs
- → Two-way client-support channel via Telegram + ERP
- → Optimized database queries: 2x+ faster data retrieval
FastAPIDjangoFlaskaiohttpKafkaKubernetesPostgreSQLRedisCouchDBSolr
Core Developer / Architect
Nagi Social Network · Israel
- → Backend from scratch for 100k+ active user social network (iOS & Android)
- → Real-time E2E encrypted group chats: <100ms latency via WebSockets
- → ML content moderation: 96% accuracy, automated inappropriate content detection
- → Blockchain-based bonus system with proprietary tokens
- → Live video streaming, infinite news feed, stories
WebSocketsRedisPostgreSQLContent Moderation
Tech Lead
Brander · Kharkiv
- → Led team of 4-5 backend developers: mentorship, code reviews, hiring
- → TCP server for 500+ IoT electric scooter devices
- → Multi-channel ERP: +30% support operator efficiency
- → B2B platform (Estel), logistics (Kangong/Canada), dating apps, e-commerce (Georgia)
- → L3 support for high-load international B2B platform qoovee.com
DjangoFlaskPostgreSQLRedisCeleryElasticsearchWebSocketsDockerEvent-Driven ArchitectureTCP ServersIoT Protocols
MSc Computational Physics
V. N. Karazin Kharkiv National University. Thinking about infrastructure as a system with measurable efficiency.
V. N. Karazin Kharkiv National UniversityFounder - BERI KATI
Electric scooter rental startup. Built from idea to revenue. Learned to look at architecture through P&L, not just test coverage.
FAQ
Common questions before reaching out.
Is Denys available for hire?
Yes, currently available for hire. Open to remote senior backend engineering roles (Python, Go), tech lead positions, AI/LLM engineering, system architecture consulting, and freelance contracts. Works remotely from Ukraine for US, EU, and Israeli teams.
How do I hire Denys?
Email hello@den.dance with a brief role or project description, or message via LinkedIn (linkedin.com/in/denindance/). Typical response within 24 hours on business days.
What services does Denys offer?
Backend development (Python, Go), system architecture and monolith-to-microservices migrations, AI/LLM pipeline development and cost optimization, IoT and hardware integration, technical consulting, code reviews, and tech lead engagements.
What is the tech stack?
Python (FastAPI, Django, aiohttp), Go (gRPC, high-concurrency services), PostgreSQL, Redis, Kafka, Celery, AWS (ECS, S3, SQS), Docker, Kubernetes, OpenAI / Anthropic APIs, LLM pipelines, RAG, TCP servers for IoT.
Why the domain den.dance?
It's not random. I dance as a hobby, and back in university I ran indance, a social-media project that grew into a community of 10,000+ active dancers (events, coverage, dance media). My LinkedIn handle (denindance) is a leftover from that era. When picking a personal domain, .dance was the obvious tie-in. Bonus: 3-letter domains usually cost a small fortune, but .dance doesn't, so I grabbed den (the first three letters of "Denys") for less than a sandwich. Reads as a verb, fits on a business card.
Hire Denys for your next project
Available for remote senior backend roles (Python, Go), AI/LLM engineering, and consulting. If a system can be measured, I can make it faster and cheaper.
hello@den.dance LinkedIn UA Kharkiv