Senior Backend Engineer (m/w/d)

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: Central Berlin — hybrid, 3 days in the office and 2 days from home. About us CarOnSale is the AI-powered platform 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. Your responsibilities 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 A proven mentorship track record: you have coached engineers and raised the standard around you Solid command of Git, Docker and C