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. Tasks As 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 flows Scalability and performance of data-heavy workflows handling millions of activity data points across complex customer organisations Setting technical direction for the Rails codebase and its long-term evolution service boundaries, data model, API surface Technical excellence across the squad: clean code, deliberate test pyramid, thoughtful API design, disciplined handling of technical debt Knowledge exchange and code quality through reviews, pairing and architectural discussions that level up everyone around you This 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 processing Drive architectural decisions for the CCF module together with the Principal, Leads and other Senior Engineers Translate product and domain requirements into robust technical solutions Identify 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 debt Set the engineering bar through hiring loops, technical interviews and onboarding You’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, Golang Data & Messaging: Postgres, Redis, ClickHouse, NATS AI & Services: Python, FastAPI, FastStream Infrastructure: Docker, Kubernetes, GitHub Actions Wh