Senior Ruby Engineer, Koinly

• We’re looking for a self-motivated individual who takes pride in their work, values high-quality code, and cares deeply about the overall application experience
• If you have a data mindset, a sharp eye for clean, scalable code, a bias for ownership, and want to work in the fast-growing crypto space, apply now!
• 5+ years of professional Ruby experience
• A CS degree (or deep hands-on background via data science or backend track)
• Strong SQL skills, including performance tuning and complex queries
• Strong problem-solving and debugging skills — you leave code better than you found it
• Experience working with RESTful APIs, microservices, and third-party integrations
• Familiarity with background job processing tools (Sidekiq, etc.)
• Proficiency in at least 2 programming languages
• Eagerness to work with a high-standard engineering team, CI/CD, and testing
• Clear, concise written and verbal communication in English
• You're based in Europe and have experience working remotely in async environments
• Comfort with feedback loops and a high-ownership mindset

Desirable

• At Koinly, we’re looking for a Senior Ruby Developer to help design, build, and maintain scalable backend systems that power crypto tax reporting for over 1.5 million crypto investors
• You’ll write clean, efficient, and high-performance code – not to just ship new features, but to continuously optimize speed, reliability, and user experience across our Ruby (and Ruby on Rails)-powered architecture
• As a Senior Ruby Developer, you’ll be responsible for writing clean, modern code that adheres to best practices
• We pride ourselves on having very high test coverage and rarely having any prod issues. Our backend follows a microservices architecture, consisting of multiple small services that collectively power the user experience
• Design, build, and maintain scalable and efficient Ruby applications
• Own and implement new product features end-to-end
• Maintain existing code while ensuring high performance and responsiveness
• Write clean, maintainable, and efficient code following best practices
• Optimize applications for performance, speed and scalability
• Implement automated tests and ensure robust code quality
• Debug and troubleshoot complex issues across production and development environments
• Work closely with product managers, designers, and other engineers in a focused async loop
• Stay up-to-date with emerging technologies and best practices in Ruby development
• May have on-call responsibilities

• An initial call with the talent team (30 mins)
• A take-home task (~3 hours)
• Technical interview with live-coding and architecture problems (90 mins)
• Final call with the founder (30 mins)