Senior Ruby Engineer

Own your work, skip the meetings, and write code that directly impacts millions of users.

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 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.

Why this role exists

We’ve hit product–market fit in a messy, high-scale domain. Now we need to keep pushing performance and reliability while shipping new features. That means solving hard problems in:

• 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.

What you’ll do:

• 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.

What you bring:

• 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.

Bonus points for:

• 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.

What you’ll get:

• A lean, no-BS engineering environment with high-trust and high-impact engineering environment with zero fluff that ships with quality.

• Flat operations with full ownership and autonomy. No unnecessary layers between you and shipping.

• An async-first work environment that favors clear communication and documentation over meetings.

• A role where every line of code you write has a direct user impact.

• A culture that values feedback, autonomy, and outcome-driven work

• USD $80–$90K per year (B2B contract).

• 32 paid days off per annum (incl. public holidays).

• Remote and async-first work environment.

• Co-working space budget, if desired.

Your first month

Your first few weeks at Koinly are all about mutual discovery. You’ll receive hands-on tasks that help us understand your technical strengths and how you operate in our async-first, ownership-driven environment. At the same time, you’ll get to explore whether our way of working challenges and supports you in the right ways.

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!

Our hiring process

1. An initial call with the talent team (30 mins).

2. A take-home task (~3 hours).

3. Technical interview with live-coding and architecture problems (90 mins).

4. Final call with the founder (30 mins).

How to apply

Ready to join a lean, async-first team building real-world tools for the crypto space? We’re looking for clarity, ownership, and technical sharpness.

Click “Apply for this job” to submit your CV.