Oleksandr — Backend Development freelancer in Ukraine

I’m a Senior Python Developer and Full-Stack Engineer with 10+ years of experience, specializing in Django, FastAPI, and scalable backend systems. My expertise covers Payment Systems, E-Commerce Platforms, API Development, and Cloud Automation, helping businesses build secure, high-performance applications that scale. 🚀 What I Offer Backend & API Development Deep expertise in Django, FastAPI, Flask for building robust web apps and async APIs Microservices & API architecture with REST, GraphQL, gRPC, WebSockets Secure auth flows with OAuth2, JWT, OpenID High-performance async programming (asyncio, multiprocessing) Payment Systems & E-Commerce Experience with crypto payments (Ethereum, BNB, Bitcoin) PCI-DSS compliant solutions with 3D Secure, tokenization, and fraud prevention Built custom e-commerce platforms and integrated Shopify, WooCommerce, Magento APIs Expertise in subscription billing, marketplaces, and headless e-commerce Databases & Scaling SQL (PostgreSQL, MySQL) & NoSQL (MongoDB, Firebase, Cassandra) ORMs: Django ORM, SQLAlchemy, Prisma Performance optimization with Redis, Memcached, Celery High-load systems (1M+ transactions\u002Fday, real-time monitoring dashboards) Cloud & DevOps Docker, Kubernetes, Terraform, AWS (Lambda, ECS, S3, CDK), GCP, Firebase CI\u002FCD with GitHub Actions, GitLab CI, Jenkins Serverless architectures for cost-efficient scalability Frontend (Full-Stack) React, Next.js, TypeScript, JavaScript UI frameworks: TailwindCSS, Material UI, Styled Components Testing with Pytest, Selenium, Postman 🏆 Case Studies & Achievements FinTech Platform (FastAPI + PostgreSQL + Redis) → Handled $20M+ annual transactions, integrated 5+ gateways. SaaS Platform (Django + React) → Used by 10M+ users, real-time data sync, role-based access. E-Commerce AI Engine → Recommendation system boosted conversions by 40%. Monolith → Microservices Migration (FastAPI + Docker + Kubernetes) → 70% downtime reduction, 5x faster deployments. Crypto-Payment Gateway (Flask + Web3.py) → Secure ETH & BNB payments for NFT marketplace. Custom Subscription Billing Engine (Django + Stripe) → Coupons, trials, pro-rata billing, analytics. 💡 Why Work With Me? 15+ years of hands-on Python & full-stack experience Expert in secure payment systems & high-load e-commerce Strong problem-solving mindset with business-driven solutions Clear communication, reliability, and deadline focus. 📬 Let’s Build Something Great Need a Python\u002FDjango expert to architect a scalable system, integrate secure payments, or optimize your e-commerce platform? Let’s talk!