Konstantin S.Private profile: Upwork shows its earnings only to signed-in members, so we check it every few weeks, not daily. MRR here is a rough estimate (Upwork's six-month earnings ÷ months active). Last read Nov 5, 2026.

Python, Django, FastAPI, PostgreSQL, AWS Lambda, API Development, REST API, API Integration, Web Scraping, Data Extraction, ETL Pipeline, OpenAI API, LangChain, Celery, Docker 5+ years, usually as the lead or only backend engineer, so I own the whole path: architecture, database, APIs, CI/CD, cloud, monitoring and support after launch. WHAT I CAN BUILD FOR YOU • Backend APIs and services: Django/DRF, FastAPI, Flask, async Python, PostgreSQL • Integrations: Stripe, Square, Twilio, Microsoft Graph, Google APIs, DocuSign, webhooks, partner REST APIs • AI and LLM features: OpenAI and Claude APIs, LangChain, pgvector, tuning for cost and accuracy • Web scraping and data pipelines: Playwright, Selenium, Scrapy, ScrapingBee, Scrapfly, anti-bot and CAPTCHA handling, ETL, deduplication • AWS: Lambda, API Gateway, SQS, DynamoDB, S3, SES, ECS Fargate, RDS/Aurora, Serverless Framework • Modernising legacy systems without losing data SELECTED RESULTS • Replaced a legacy .NET finance system with FastAPI, Celery and PostgreSQL. Ran both systems in parallel and matched revenue to the cent for 2+ months before switch-over. 650 automated tests. • Built the AWS serverless backend of a privacy SaaS covering 100+ data-broker sites. Scaled to 50K+ concurrent requests at 99.9% uptime. Top contributor with 1,000+ commits. • Ran data ingestion from 500+ sources with canary checks and per-source alerting. • Rebuilt an OpenAI realtime voice integration, cutting latency from 5 to 7 seconds to under 2. • Cut LLM spend 65% by restructuring prompts and moving work to cheaper model tiers, with accuracy measured per tier. • Energy-cost platform evaluating 10K+ building scenarios ($500K+ in modeled client savings). Introduced Kafka and cut database size 30%. HOW I WORK • Clear estimates up front, and I tell you early if something is at risk • Tests and CI on every project, plus documentation the next developer can use • Regular written updates. I'm in UTC+6, which overlaps US mornings and the full European working day • AI-assisted development with Claude Code, with every change reviewed by me