Senior Ruby Engineer, Koinly

• 6+ years of professional Ruby experience
• Strong SQL skills, including performance tuning and complex queries
• Strong problem-solving and debugging skills
• Experience designing and scaling backend systems (microservices, APIs, background jobs)
• Eagerness to work with a high-standard engineering team, CI/CD, and testing
• A track record of taking full ownership of complex features or systems
• Clear, concise written and verbal communication in English
• Comfort with feedback loops and a high-ownership mindset

Desirable

• We need an engineer who thinks in data pipelines, indexes, and execution plans, not just models and controllers
• Someone who gets irrationally motivated by shaving milliseconds off a query, or turning an hour-long CSV import into minutes
• We’re a fully remote-first, async-first startup with product-market fit in a niche (and booming) domain: crypto taxes
• If you value autonomy, technical excellence, and clear communication over meetings and process complexity, Koinly is the place for you
• Data architecture: Making billions of rows and massive CSVs play nicely with high-throughput APIs
• Performance optimization: Query tuning, caching strategies, background job orchestration
• System design: Scaling Ruby microservices that process terabytes of data without falling over
• Own backend services end-to-end — design, build, refactor, and optimize
• Work with huge datasets (billions of transactions) and make them fast, reliable, and cost-efficient
• Debug gnarly production issues that live at the intersection of code, data, and infrastructure
• Write clean, tested, maintainable Ruby that holds up under scale
• Champion performance, clarity, and simplicity in code and system design
• Occasionally take part in on-call rotation (we have very few prod issues — high coverage and careful releases are the norm here)
• Stay up-to-date with emerging technologies and best practices in Ruby development
• Reporting to: Tech Lead
• Contract type: Full-time (Contractor - B2B)

• Start date: ASAP