Support Engineer (L3) at Lago (S21) €70K - €100K EUR Open Source Metering and Usage Based Billing Paris, IDF, FR / Paris, Île-de-France, FR / Remote 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, Kafka, Ruby on Rails, SQL 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. Overview At Lago, Support Engineers are core engineers operating at the edge of production. They debug real customer environments, ship fixes, and ensure Lago runs reliably at scale. This is not a ticketing function: it’s hands-on software engineering. You’ll dive into Ruby on Rails, PostgreSQL, Redis, Kafka, Clickhouse and our React + TypeScript front-end to find, fix, and prevent production issues. You’ll collaborate daily with Core Engineering, Product, and Forward-Deployed teams to turn every customer interaction into product insight and reliability improvement. You own reliability. You fix what’s broken. You strengthen the system for everyone. What you’ll be doing Investigate, reproduce, and resolve production issues across Lago’s stack: Rails backend, APIs, integrations, and React front-end. Ship code-level fixes or patches directly to production, in collaboration with Core Engineering when needed. Perform root-cause analysis for incidents and propose preventive improvements. Review customer or partner pull requests (e.g., private billing integrations) and ensure safe merges. Contribute to observability by improving logs, tracing, and alerting coverage. Participate in post-mortems, reliability reviews, and debugging playbook improvements. Mentor L1/L2 engineers on debugging, reproducibility, and communication best practices. Build or enhance internal tools and automations to prevent recurring issues. Who you are An experienced Ruby on Rails engineer (or strong polyglot dev eager to master Rails). Familiar with PostgreSQL, Redis, Sidekiq, and Kafka. Skilled at debugging production systems: reading logs, tracing jobs, inspecting payloads, and writing diagnostic scripts. Comfortable with React + TypeScript front-end debugging (or eager to learn it). Understands APIs, data consistency, and event-driven architecture. Calm under pressure and clear in communication: especially during incidents. Obsessed with prevention, documentation, and reliability. Who you’re not You don’t view “support” as reactive work: you see it as engineering in production. You don’t just hand off bugs: you fix them or make them preventable. You don’t dismiss customer issues: you use them to improve the product. You don’t operate in isolation: you collaborate across engineering, product, and customer teams. Requirements 6+ years of experience as a software engineer (Rails preferred). Proficiency in Ruby, SQL, and debugging live production systems. Experience with background job frameworks (e.g., Sidekiq) and message queues (Kafka a plus). Familiarity with REST APIs, webhooks, and data integrations. Understanding of containerized environments (Docker, AWS, CI/CD). Excellent 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, event-driven architecture, or developer tools. Experience with observability stacks (e.g., Datadog, Grafana, Sentry). Exposure to frontend debugging in React and TypeScript. Growth path Technical: Senior Support Engineer → Staff Reliability Engineer → Core Engineering. Cross-functional: Forward-Deployed Engineer (integrations) or Product Engineer. Leadership: Support Engineering Lead or Reliability Lead. At Lago, Support Engineers are our reliability champions: engineers who see production truth and make the entire product better. Why Join Lago You’ll join a lean, high-impact team that values clarity, speed, and craftsmanship. Your work will immediately matter: helping real customers succeed with our billing infrastructure. You’ll help shape processes, tools, and culture from the ground up, not just plug into a rigid system. If you love debugging complex systems, delighting developers, and scaling operations from zero to hundreds of customers: this is for you. 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. Technology Back-end: Ruby, Postgres, AWS Front-end: .js, React, GraphQL, Typescript