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 including Y Combinator and FirstMark, reflecting strong confidence in our vision and growth. Our platform has garnered over 9,000 stars on GitHub, a testament to our active and growing developer community. Companies such as PayPal, CoreWeave, Synthesia and Mistral.ai choose 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.
We're looking for a Senior Backend Ruby Engineer to contribute to Lago's core product and help scale our open-source billing infrastructure. You'll work across the full backend stack, collaborate closely with Product and Frontend, and help shape how we build and evolve the platform.
Contribute daily to all parts of our codebase, using our development workflow
Tackle a wide variety of technical problems throughout the stack
Help grow the back-end team
Work with our Product Team and Front-end Engineers to understand customer needs and challenges
Come up with technical solutions to create and improve our best features and architecture
Strong knowledge of Ruby (at least 6 years hands-on experience)
Experience working with large volumes 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!
A real appetite for the early stages of co-creating a product and shaping Lago's future
Bonus: you've worked on billing or tax projects — whether implementing a billing system, maintaining it, or integrating it with business tools (e.g. a CRM, Finance tools)
You're not looking for a "just ship it" culture without quality standards — we care deeply about both speed and craftsmanship
You're not someone who works in silos — you actively collaborate with Product, Frontend, and your fellow engineers
You're not intimidated by ambiguity — early-stage problems don't always come with a clear spec, and you're comfortable navigating that
You're not allergic to context-switching — in a lean team, priorities shift and you adapt without losing momentum
6+ years of hands-on experience in software engineering, with strong Ruby expertise
Experience working with event-driven systems and high-data-volume environments
Familiarity with background job frameworks (e.g. Sidekiq) and message queues
Comfort with REST APIs, webhooks, and data integrations
Strong written and verbal communication skills
A mindset of ownership, curiosity, and resilience
Nice to have
Experience contributing to or supporting open-source projects
Familiarity with billing systems, fintech, or developer tools
Experience with PostgreSQL, Redis, Kafka, or similar infrastructure
Exposure to containerised environments (Docker, AWS, CI/CD)
Work with top-tier talent: Join a team that values excellence, ambition, and accountability
Shape the future of fintech: Be part of a fast-growing company building the best open-source billing platform
Remote-friendly: Work from anywhere in Europe (within +2h/-2h of CET), or join us in our Paris office
Competitive package: Competitive salary and equity for employees based in France
Make an impact: Your work directly shapes the product used by companies like PayPal, Synthesia, and Mistral.ai
Ready to Build with Us? If you're excited about joining a high-talent team to solve meaningful problems and help businesses thrive, we'd love to hear from you. Apply today and let's build something remarkable—together.
Location type: Remote
Primary Location: Remote Europe
Team: Product Engineering
Work Type: Full Time/Permanent Contract
Salary: 70,000–100,000 EUR per year
(Applicants must be based in the location specified for this role. Applications from other locations will not be considered.)
Lago