Senior Back-end Ruby Engineer at Lago (S21) €60K - €100K EUR Open Source Metering and Usage Based Billing Paris / Remote (FR; PT; GB; NL; ES; IT; DE; RO; PL; BG; EE; BA; CA; MX) Full-time US citizenship/visa not required 6+ years About Lago At Lago, we’re on a mission to make billing simpler, more transparent, and more adaptable for SaaS companies. As the leading open-source billing platform, we empower businesses to build flexible pricing models and scale with confidence. We’ve raised over $22 million in funding from top-tier investors, reflecting strong confidence in our vision and growth. Our platform has garnered over 8,000 stars on GitHub, a testament to our active and growing developer community. Next-gen companies such as Mistral.ai, Groq, and Laravel chose Lago for their billing. We’re a team of ambitious, focused individuals who work together to solve hard problems with excellence and accountability. At Lago, we value reliability and proactivity—we trust each other to own tasks, drive them to completion, and adapt quickly. While we encourage you to try fast and “fail fast”, we also expect you to learn fast: make mistakes, but don’t make the same one twice. If you’re excited by challenges and want to grow alongside a high-performing, supportive team, this is the place for you. About the role Skills: Ruby, Ruby on Rails, PostgreSQL About Lago At Lago, we’re on a mission to make billing simpler, more transparent, and more adaptable for SaaS companies. As the leading open-source billing platform, we empower businesses to build flexible pricing models and scale with confidence. We’ve raised over $22 million in funding from top-tier investors, reflecting strong confidence in our vision and growth. Our platform has garnered over 8,000 stars on GitHub, a testament to our active and growing developer community. Next-gen companies such as Mistral.ai, Groq, and Laravel chose Lago for their billing. We’re a team of ambitious, focused individuals who work together to solve hard problems with excellence and accountability. At Lago, we value reliability and proactivity—we trust each other to own tasks, drive them to completion, and adapt quickly. While we encourage you to try fast and “fail fast”, we also expect you to learn fast: make mistakes, but don’t make the same one twice. If you’re excited by challenges and want to grow alongside a high-performing, supportive team, this is the place for you. What you’ll do Contribute daily to all parts of our code base, using our development workflow Tackle a wide variety of technical problems throughout the stack Help grow the back-end team Work with out Product Team, and our Front-end Engineers to understand customer needs and challenges And come up with technical solutions to create and improve the best features, and our architecture The ideal candidate will have Strong knowledge of Ruby (at least 6 years hands-on experience) Experience working with lots of data and event-driven environments A genuine passion for Open-Source: if you’ve contributed to OSS projects or used OSS tools, let us know! Bonus: you’ve worked on billing or tax projects: whether it was to implement a billing system, or maintain it, or integrate it with business tools (e.g., a CRM, Finance tools) A real appetite for the early stages of co-creating a product and shaping Lago's future We offer a competitive package including equity for employees based in France, we're remote-friendly, and organize regular workations usually by the ☀️🌊🏄♀️ Location: EU (+2h/-2h from Paris) This role is based either in-office in Paris in our gorgeous new office in the 10th arrondissement, and/or remote in a timezone that is +2/-2h from CET. Learn more how we think and work Open-source does not win by being cheaper Post-mortem of our 1st YC startup: a Reverse ETL How soon should you have a design system? How we ship fast: our framework Technology Back-end: Ruby, Postgres, AWS Front-end: .js, React, GraphQL, Typescript