Ruby Engineer

Process billions of rows, optimize massive datasets, and tackle complex database challenges. Join Koinly to push Ruby and SQL performance to the limit in a high-scale, async-first environment., * Main responsibilities: Design, optimize, and scale Ruby backend services handling billions of records, ensuring performance, reliability, and clean code at massive scale.

• 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.
• Comfort with feedback loops and a high-ownership mindset., * Experience with high-volume CSV/data ingestion pipelines.
• Familiarity with performance profiling tools in Ruby.
• Background in DeFi, blockchain, or fintech.
• Side projects that show your love for technical puzzles.

• Ruby/Rails isn't your main language or only occasional experience.
• Limited backend ownership, system design, or microservices experience.
• Rails work mostly UI/features with light SQL, no pipeline/data/query optimization.
• Exclusive infra/SRE or app-only focus, lacking hybrid backend/data skills.
• Prefer structured processes, frequent meetings, or struggle with async work.
• Dislike ambiguity, messy, or inconsistent data.
• Juggling multiple part-time roles; can't commit full-time.

At Koinly, we're hiring a Senior Ruby Developer to build and maintain scalable backend systems for over 2 million crypto investors. You'll write high-performance Ruby/Rails code and continuously improve speed, reliability, and the overall user experience. We're looking for someone who excels at performance and data at scale, is comfortable with queries, indexes, and large imports, and is motivated to make systems faster and more efficient. We're a profitable, bootstrapped, remote-first startup founded in 2018 with a strong product-market fit in the fast-growing crypto tax space. If you value autonomy, high engineering standards, and clear communication over heavy process and meetings, you'll fit right in at Koinly., About Koinly We're on a mission to simplify crypto taxes and asset tracking. * We are one of the fastest-growing crypto tax calculators in the world with solid product-market fit. * Trusted and loved: don't take our word for it, see what our customers say. * Used by hundreds of thousands of investors and accountants, and a partner to major crypto exchanges. Our users get through their crypto taxes in 20 minutes; many will save days or weeks, filing their crypto taxes for the first time, giving them the confidence to build a portfolio for the long term. We are building tools to enable further widespread adoption of cryptocurrency by automating the regulatory hurdles of tax compliance and asset tracking. Founded in 2018 Co-workers 40 Tech · London · Fully Remote