Senior Backend Engineer (f/m/x)

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

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

• 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