I`m Roman Sapezhko
Web Engineer

Enhanced Django/Postgres/Redis digital goods platform, optimizing queries and caching, boosting transaction throughput by 35%. Built marketing and analytics tools, reducing report generation time from 4 hours to 15 minutes, improving decision-making efficiency. Developed internal APIs with 99.9% uptime, implementing rate-limiting and real-time dashboards supporting 500+ requests/sec. Designed, deployed, and monitored Dockerized production environments; configured CI/CD pipelines reducing deployment time by 65%. Implemented unit and integration tests for API endpoints and background tasks, achieving 90% code coverage, ensuring stability under high load.

Developed IoT warehouse box rental system with recurring subscriptions, increasing customer retention by 20%. Re-architected payment system with secure API design and data handling, reducing support tickets by 60%, ensuring compliance with GDPR principles. Integrated Orange Pi for automated door control, achieving 99.8% uptime and real-time status reporting. Processed thousands of IoT messages via RabbitMQ and Celery, handling 2,500+ messages/min with 99.9% delivery. Built APIs for rental management, monitoring, and device alerts, reducing response time from 15 minutes to 30 seconds. Added unit and integration tests for workflows and payment processing, reducing critical bugs by 70%.

Developed multi-tenant backend infrastructure supporting 10,000+ users. Built REST APIs for site creation, user management, and subscription handling with 99.9% uptime. Integrated payment systems and recurring billing, reducing payment failures by 40%. Implemented CRDT backend for real-time collaborative editing, enabling simultaneous editing by up to 15 users. Implemented Celery and RabbitMQ for background tasks, scaling 1,500+ operations/min. Wrote unit and integration tests for APIs, subscriptions, CRDT workflows, and background tasks.

Developed recurring payments and subscription management system with Django/PostgreSQL, supporting 5,000+ active subscriptions. Built REST APIs for client interaction, monitoring, and automated billing. Integrated Celery and RabbitMQ for high-throughput job queues, handling 1,000+ operations/min. Implemented automated tests for payment flows and APIs, achieving 85% code coverage.

Developed speed-limiting and zone control for scooters using Django/Postgres GIS, improving rider safety in high-traffic areas. Processed orders in threads for concurrency, handling thousands of requests/sec. Implemented real-time telemetry via RabbitMQ for thousands of devices simultaneously. Automated monitoring and alerts, reducing downtime by 20%. Designed event-driven architecture for scalable order processing. Added unit and integration tests for order processing, threading logic, and telemetry.

Developed OpenCV module to automatically read meters from photos, processing 2,000+ readings/day. Integrated backend APIs for ingestion and verification. Wrote unit tests for image processing functions and API integration, reducing errors by 25%.

Collected, processed, and visualized real-time IoT data using Django, Celery, and RabbitMQ, supporting 1,000+ devices. Controlled functional parameters of connected devices remotely. Built APIs for dashboards, alerts, and high-throughput telemetry processing. Implemented unit and integration tests for data ingestion and alert logic, reducing system errors by 15%.