Senior Backend Engineer - Ruby on Rails (m/f/d)

Are you tired of working on products you don’t really care about?Do you want to work on something that has a positive impact on humanity and our planet? Do you like to get stuck in and are you passionate about coding? Then we have a great opportunity for you.At Global Changer, you will work on a solution with a clear goal: helping companies reduce emissions faster. We focus on one of the biggest levers to fight the climate crisis and work mainly with large organisations.We are backed by well-known investors (including neosfer, part of the Commerzbank Group, and the former CIO of innogy) and work with renowned customers such as Heraeus, Görtz and Haniel.Our goal is to reach as many companies as possible worldwide with our software and contribute meaningfully to reducing emissions. Impact is therefore one of our core values.About the software:Our product is a SaaS B2B platform that supports companies along their sustainability journey, with a strong focus on carbon accounting (Corporate Carbon Footprint (CCF) and Product Carbon Footprint (PCF)). We use AI to support data-heavy workflows and to generate estimates where data is incomplete, always with the goal of improving data quality over time.TasksAs a Senior Backend Engineer - Ruby on Rails (m/f/d), you will shape the backbone of our Corporate Carbon Footprint (CCF) module.Your focus is on backend architecture and domain modeling for one of the most data- and audit-relevant problem spaces in enterprise software: corporate emissions accounting under the GHG Protocol. You design, build and evolve the Rails services that sustainability professionals at large organisations with a huge amount of data rely on to produce reportable, defensible numbers.This is a hands-on senior role with significant architectural responsibility. You set the bar for code quality, scalability and long-term maintainability of our backend and lift others up to meet it.You will work closely with the product management, lead and senior engineers as well as sustainability experts, combining hands-on implementation with architectural responsibility.You will work on:Backend architecture and domain modeling for the CCF module for Scope 1, 2 and 3, emission factor matching, calculation engines and reporting flowsScalability and performance of data-heavy workflows handling millions of activity data points across complex customer organisationsSetting technical direction for the Rails codebase and its long-term evolution service boundaries, data model, API surfaceTechnical excellence across the squad: clean code, deliberate test pyramid, thoughtful API design, disciplined handling of technical debtKnowledge exchange and code quality through reviews, pairing and architectural discussions that level up everyone around youThis is not a generalist role. We are looking for someone who is genuinely excellent at Ruby on Rails and wants to apply that depth to a domain where it matters. Tasks:Own backend services in our Rails codebase end-to-end from data model over API to background processingDrive architectural decisions for the CCF module together with the Principal, Leads and other Senior EngineersTranslate product and domain requirements into robust technical solutionsIdentify and remove performance bottlenecks in data-intensive workflows (Postgres query and schema design, background jobs, caching strategy)Lead by example on code quality via reviews, refactoring, principled trade-offs around technical debtSet the engineering bar through hiring loops, technical interviews and onboardingYou’re a great fit if you do understand the benefits and limitations of ActiveRecord knowing when to break with strict DHH-orthodoxy in the favour of raw Postgres performance without compromising on data-consistency.Technologies we use:Backend: Ruby on Rails, GolangData & Messaging: Postgres, Redis, ClickHouse, NATSAI & Services: Python, FastAPI, FastStreamInfrastructure: Docker, Kubernetes, GitHub ActionsWhat matters most is deep Ruby on Rails expertise and strong backend fundamentals.Requirements7+ years of experience in backend software development with battle-proven Ruby on Rails expertiseExpert-level Ruby on RailsDeep experience with Postgres at scale: schema design, query optimisation, indexing strategy, migrations on live dataTrack record of designing and evolving backend systems in data-heavy production environmentsFluent in English, clear written and verbal communication (German is a plus)You live in the EU (CET ±1) with a valid work permitYou are passionate about the fight against the climate crisis and creating customer-oriented solutions that deliver real added valueNice to have:Startup or scale-up experienceExperience in data-heavy or audit-relevant domainsExpertise in ClickHouse, CDC, KubernetesDegree in computer science or a related fieldBenefitsCreating long-lasting software with a positive impact - we are here to stayPlay a decisive role in shaping our product and corporate cultureA mission that drive