Senior Ruby Engineer | Remote-first; Europe | Crypto Tax

Senior Ruby Engineer | Remote-first (Europe only) | Crypto Tax

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.

We’re a fully remote-first, async-first startup with product-market fit in a niche (and booming) domain: crypto taxes. Our lean team of 35 people (10 in engineering) is mostly spread across EMEA. We value autonomy, technical excellence, and clear communication over meetings and process complexity.

• Department: Tech
• Location: Must be based in Europe
• Salary: USD $80,000-$90,000 per year
• Timezone: Ideally UK ±2 hours
• Team size: 10 engineers in a 35-person team

We’re on a mission to make crypto taxes simple.

Since 2019, we’ve grown to 1.5M+ users by tackling one of crypto’s messiest challenges: tax reporting. Our platform helps investors stay compliant, track their assets across hundreds of wallets, exchanges, and DeFi platforms, and save hours of time. Just see what our customers have to say about us.

Behind that focus towards simplicity lies a deeply technical product, built on large-scale data processing and integrations with hundreds of platforms. Our stack is Ruby-heavy, our test coverage is high, and our expectations on code quality and system performance are even higher.

If you’re someone who thrives on autonomy, enjoys a tight feedback loop with product, values radical candor within the team, loves building clean, efficient systems without unnecessary meetings — Koinly is what you’re looking for.

• A team that punches far above its size: 10 engineers powering a product used by 1.5M+ people.
• No fluff, no chaos. Just clean systems, deep focus, and real outcomes.
• We operate on radical candor, async documentation, and trust.
• Engineering is central to the product — not a service layer.

As a Sr. Ruby Developer, you’ll be responsible for writing clean, modern code that adheres to best practices. 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.

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.

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!

• 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.

• 5+ years of professional Ruby experience.
• 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 favor asynchronous work over meetings.
• You're based in Europe and have experience working remotely in async environments.
• Comfort with feedback loops and a high‑ownership mindset.
• Interest in…