Senior Backend Engineer (f/m/x) | Berlin
You don't want another role where someone else owns the architecture and you own the tickets. Here you pick the technology, design the architecture, and set the standards the backend runs on. 40,000 buyers. 20+ countries. 130,000 vehicles sold a year through one auction backend, and you decide how it scales.
Location: Berlin-Schöneberg — hybrid, 3 days office / 2 days remote
About us
CarOnSale is the AI-powered operating system for B2B used car trading in Europe. Over 40,000 buyers from more than 20 countries trade on our platform, and 85% of inventory is exclusive to us. We connect software, pricing intelligence, logistics and financing in one layer — as the operating system for an entire industry.
One Platform. One Profit Engine.
What you own
- You own backend development end to end: technology selection, architecture design, and implementation of the features that carry platform performance and scale
- You build AI-first. Coding agents, LLMs and AI-assisted development are part of the daily workflow here, not a pilot project
- You set the standards: code quality benchmarks, development practices, and CI/CD pipelines, agreed cross-functionally and enforced in review
- You mentor the engineers around you, share what you know, and raise the bar on backend practice
- You challenge how we work. When our approach is wrong, you say so and you bring the better one
What you bring
- 8+ years in software engineering, 5+ of them focused on backend
- Deep TypeScript proficiency, with strong Node.js, NestJS and PostgreSQL experience
- Proven mentorship track record — you have coached engineers and raised the standard around you
- Solid command of Git, Docker and CI/CD pipelines
- Comfortable in Scrum or Kanban, working with JIRA and Confluence
- English at C1 level or above, written and spoken, for daily work with an international team
- AI-native working style — you use AI tools in your own development workflow and have real judgement about where they accelerate you and where they don't
- Based in Berlin or ready to relocate
Nice to have:
- WebSockets or other real-time systems
- Search frameworks such as Elasticsearch or Lucene
- Automotive or B2B trading background
- Conversational German
What you get
- Hybrid working — 3 days in our Berlin-Schöneberg office, 2 days remote
- Architecture ownership from day one, not after a probation period
- 28 days annual leave
- Company pension with 20% employer contribution
- Subsidised Deutschlandticket
- FitX or Urban Sports Club membership subsidy
- Structured onboarding with buddy programme
- An engineering culture where AI tooling is embedded in how the work gets done
- Direct access to the full European engineering team
- Backing behind the platform you build on: founded 2018, 400 people, €70M Series C in July 2025 led by Northzone and HV Capital
Skills Required
- 8+ years in software engineering, with 5+ years focused on backend
- Deep TypeScript proficiency
- Strong Node.js and NestJS experience
- PostgreSQL experience
- Proven mentorship track record (coached engineers)
- Solid command of Git, Docker and CI/CD pipelines
- Comfortable in Scrum or Kanban; experience with JIRA and Confluence
- English C1 level or above (written and spoken)
- AI-native working style; uses AI tools in development with sound judgment
- Based in Berlin or ready to relocate
- WebSockets or other real-time systems
- Search frameworks such as Elasticsearch or Lucene
- Automotive or B2B trading background
- Conversational German
What We Do
Our vision is to make automotive wholesale frictionless across Europe. We developed an innovative marketplace to connect buyers and sellers. We are ambitious, digital and reliable. We are committed to provide our customers with the easiest, most profitable and personal solution. Together with our ambitious team, we set new standards in the remarking of used cars. We are looking for talents who believe in our vision and support us in the digitization of automotive wholesale. If you are looking for a place to realize your full potential and grow beyond your limits - COS is your place! CarOnSale (Castle Tech GmbH) Hauptstraße 27 Haus 9 Aufgang N 10827 Berlin Managing Director: Tom Krüger Phone: +49 30 311 96 400 E-Mail: [email protected] Registry court: Charlottenburg Local Court (Berlin), HRB 213350 B Sales tax identification number according to §27a Umsatzsteuergesetz: DE320199054 Tax number: 241/123/11331 Privacy policy https://www.caronsale.com/de/datenschutz
