Available to hire
Hi, I’m Rostyslav Popadyn, a senior full-stack software engineer with 10+ years of experience building scalable, high-performance web applications and distributed systems. I specialize in Ruby on Rails, Python (Django, Flask, FastAPI), and modern JavaScript frameworks (React, Next.js), delivering end-to-end SaaS solutions and robust RESTful/GraphQL APIs.
I focus on clean, maintainable architectures, CI/CD, and cloud-native deployments across AWS, Azure, and GCP. I enjoy collaborating with product and frontend teams to ship reliable software and optimize production performance.
Skills
Experience Level
Expert
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Language
English
Fluent
Russian
Fluent
Ukrainian
Fluent
Work Experience
Senior Full-Stack Developer at Upwork.com
August 1, 2019 - PresentDesigned and deployed multiple Python/Django REST APIs and event-driven microservices for fintech and healthtech clients. Built scalable backend systems using Python, Flask, and FastAPI integrated with PostgreSQL and MongoDB. Managed Kubernetes deployments (AKS/EKS) with zero downtime, implementing Helm charts and CI/CD pipelines via Azure DevOps & GitHub Actions. Automated infrastructure provisioning using Terraform for multi-cloud environments (AWS, Azure). Integrated monitoring with Prometheus/Grafana, implemented logging best practices, and optimized API performance by 40%.
Senior Ruby on Rails Developer at Web DevStar -LLC
October 1, 2024 - PresentDesigned and developed scalable Ruby on Rails applications, including RESTful APIs and SaaS platforms. Built backend systems using Rails, PostgreSQL, and Redis, ensuring performance and reliability. Implemented background job processing with Sidekiq for asynchronous workflows. Structured applications using MVC architecture, ActiveRecord, and service-oriented design. Integrated third-party services (Stripe, analytics, external APIs) and implemented secure authentication (JWT, OAuth2). Deployed and scaled applications using Docker, Kubernetes, AWS, and Azure. Optimized database queries and application performance, improving response times and system efficiency. Collaborated with frontend teams (React/Next.js) to deliver full-stack solutions.
Senior Backend Developer at Open-Cosmos
June 1, 2024 - September 30, 2024Led the modernization of a satellite data platform by architecting and implementing a distributed microservices system using .NET 7 and Golang, enabling high-availability telemetry data processing across multiple regions. Designed and developed event-driven services using Azure Functions (Durable & Timer Triggers) to handle large volumes of space-borne sensor data with precision timing and fault tolerance. Collaborated closely with DevOps to implement infrastructure-as-code (IaC) using Terraform, optimizing CI/CD pipelines in Azure DevOps for weekly, zero-downtime deployments. Integrated Azure Key Vault, Managed Identities, and secure API gateway patterns to enforce compliance with aerospace-grade security standards. Mentored a distributed backend team on clean architecture principles, logging/monitoring strategies, and test automation. Introduced data validation and normalization routines in Golang for satellite payloads, reducing ingest processing time by 30%.
Senior Backend Developer at Ciklum
March 1, 2024 - June 30, 2024Developed Python-based ingestion pipelines for aggregating and normalizing data from external APIs into Snowflake. Deployed and managed Kubernetes workloads with horizontal scaling for high-volume data processing. Built REST APIs in Python and Golang, ensuring secure authentication and data validation. Automated deployments using Terraform and Azure DevOps.
Senior Ruby on Rails Developer at Web DevStar LLC
October 1, 2024 - PresentDesigned and developed scalable Ruby on Rails applications, including RESTful APIs and SaaS platforms. Built backend systems using Rails, PostgreSQL, and Redis, ensuring performance and reliability. Implemented background job processing with Sidekiq for asynchronous workflows. Structured applications using MVC architecture, ActiveRecord, and service-oriented design. Integrated third-party services (Stripe, analytics, external APIs) and implemented secure authentication (JWT, OAuth2). Deployed and scaled applications using Docker, Kubernetes, AWS, and Azure. Optimized database queries and application performance, improving response times and system efficiency. Collaborated with frontend teams (React/Next.js) to deliver full-stack solutions.
Senior Golang Backend Developer at Shipa.io
January 1, 2023 - December 31, 2023Led migration from monolith to containerized microservices in Python and Go, orchestrated with Kubernetes and Helm. Created Terraform modules to provision cloud infrastructure. Implemented Prometheus-based monitoring and alerting systems for production workloads.
Senior Lead Blockchain Developer at BT Medical/ Strawman Dental
August 1, 2020 - December 31, 2022Led blockchain system architecture for a decentralized healthcare platform integrating smart contracts, encrypted messaging, and on-chain medical record indexing. Designed and implemented Subnet 27 on Bittensor, introducing advanced cryptographic mechanisms and zero-knowledge proof-based access control. Developed secure, high-throughput blockchain infrastructure in Golang for decentralized validator consensus and fault-tolerant peer-to-peer messaging. Architected on-chain/off-chain synchronization modules using Node.js and Solidity, ensuring data integrity and verifiability across tenants. Oversaw full-stack delivery cycles, coordinated compliance with Canadian health data standards, and optimized transaction costs by 35%.
AI and Security Specialist at Vic.ai
September 1, 2019 - June 30, 2020Researched and developed blockchain-based models for secure ledgering of invoice and expense data using Ethereum and Go-Ethereum stacks. Built and tested custom staking protocols, security tokens, and smart contracts, simulating hostile conditions to harden consensus performance. Integrated cryptographic primitives into blockchain modules and collaborated with cryptographers to ensure AES, SHA-256, and elliptic curve compliance. Developed blockchain forensic scripts in Golang to trace wallet histories, identify gas-optimized paths, and enhance fraud detection.
Backend Software Engineer at Payfluent.io
January 1, 2017 - June 30, 2019Designed a decentralized payment orchestration system using Golang and Node.js, supporting real-time transfers and validator verification. Built a DVT (Distributed Validator Technology) stack from the ground up for Ethereum-based chains, supporting secure message-passing and consensus under Byzantine conditions. Developed core modules for key management, peer discovery, and encrypted broadcasting using libp2p, BLS, and RSA.
Education
Bachelor’s Degree at State University Lviv Polytechnic
January 11, 2030 - April 1, 2012Diploma at Lviv Academy of Commerce
January 11, 2030 - April 1, 2017Bachelor’s Degree at State University Lviv Polytechnic
January 11, 2030 - April 1, 2012Bachelor’s Degree at Lviv Academy of Commerce
January 11, 2030 - April 2, 2017Qualifications
Web Development w/ Google’s Go (Golang) Programming Language
January 11, 2030 - April 18, 2026AWS Certified Solutions Architect – Associate
January 11, 2030 - April 18, 2026Blockchain Security Professional
January 11, 2030 - April 18, 2026Certified Associate JavaScript Programmer Certification
January 11, 2030 - April 18, 2026Certified Associate in Python Programming
January 11, 2030 - April 18, 2026Web Development w/ Google's Go (Golang) Programming Language
January 11, 2030 - April 19, 2026AWS Certified Solutions Architect – Associate
January 11, 2030 - April 19, 2026Blockchain Security Professional
January 11, 2030 - April 19, 2026Certified Associate JavaScript Programmer Certification
January 11, 2030 - April 19, 2026Certified Associate in Python Programming
January 11, 2030 - April 19, 2026Industry Experience
Software & Internet, Computers & Electronics, Professional Services, Media & Entertainment, Financial Services, Healthcare, Other
Led the design and development of scalable web applications and distributed systems for fintech, blockchain, and data-driven platforms. Built high-performance backend services, APIs, and microservices while ensuring reliability, security, and scalability across cloud environments.
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