Senior Full Stack Engineer

About Climax Climax is building the financial grade infrastructure for carbon accounting. We help portfolio managers, financial institutions and enterprise groups understand and manage emissions across complex portfolios of companies. That means turning messy data from financial systems, operational tools and external sources into numbers people can actually trust, audit and act on. From an engineering perspective, this creates interesting problems: integrating fragmented data sources, modelling complex calculations, building audit trails and reconciliation workflows, and making large amounts of sustainability data understandable through fast, intuitive interfaces. We're a small team, so engineers don't just implement tickets. You'll work across the stack, talk directly with the people using the product, make product and architecture decisions, and own features from the underlying data model through to the final UI. Our goal is simple: make carbon accounting as reliable and usable as financial accounting, and build the software that helps companies make better decisions about their impact. Your Role As a Full Stack Engineer at Climax, you'll have a big influence on both the product we build and how we build it. You'll own features end to end, from shaping the problem and designing the underlying data model to building the API and polishing the final interface. You'll work across our Django and NextJS stack on problems involving complex calculations, large datasets, integrations and workflows where accuracy and traceability really matter. You'll work closely with the founders and the rest of the team to turn customer problems into simple, reliable product experiences. We expect you to challenge requirements, make pragmatic scoping decisions and improve the architecture when you see a better way forward. We're a small team, so there are few boundaries around what you can own. If something is slow, fragile, confusing or unnecessarily manual, you'll have the freedom to fix it. This is a role for someone who wants to build serious software, ship quickly and have a meaningful say in the product rather than simply work through a backlog. What we're looking for 7+ years of full-stack engineering experienceExperience with Django and TypeScript (NextJS)A track record of owning complex product areas end to endExperience building software where numbers get signed off: accounting, audit, fintech or ERP. You know why period close, restatement and audit trails are hardA feel for dense data interfacesInterest in climate tech and sustainabilityComfortable working from Rotterdam in a hybrid setup Nice to have AI/LLM features in production, including how you knew they got betterIntegrations with accounting or ERP systems: incremental sync, reconciliation, schema driftFamiliarity with CSRD/ESRS or sustainability reportingExperience with GCPStartup experience About you Product-minded generalist who enjoys working across engineering, product and operationsComfortable making scoping calls without a PM, and defending what you cutSelf-driven, ambitious and naturally curiousYou move toward the parts of a product you know least wellEnjoys small teams and practical solutions Our process We keep the process practical and focused on what it’s actually like to work together: 30 min intro call2-hour technical & product deep diveTeam lunch/drinksIf it’s a match: an offer within 24 hours to join Climax. We move quickly and won’t drag you through unnecessary rounds.