Senior Ruby on Rails Developer

Oleksii Neishchenko is a Senior Ruby on Rails developer with 11+ years of experience across fintech, SaaS, e-commerce, and startups. He is open to full-time remote or contract work. His strengths include performance optimization on existing codebases (e.g., optimizing Rails API endpoints from 90-120s down to 1-2s using raw SQL, indexing, and background job restructuring), external API integrations (5+ over his career, including Google Maps, Chargebee, WhatsApp via 360dialog, SDB Groep, AFAS), and handling complex scenarios like retries, idempotency, webhook ordering, and partial failures. He is comfortable working with legacy code and untestable systems, emphasizing reading before writing and refactoring without introducing breaks. As a Tech Lead at clevergig for 3 years, he established code review, bug tracking, and ownership processes. His recent work includes FastCTO, Rail Europe, Fitjourney.ai, Kagi (Crystal backend), and clevergig. For a hobby, he built a Rails app with an ESP32 device to track power outages, demonstrating his ability to combine backend development with hardware.