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# Backend Engineer - Ranking Systems

- **Company:** Bertelsmann SE & Co. KGaA
- **Location:** Hamburg, Germany
- **Experience:** Expert
- **Contract:** Permanent contract
- **Skills:** Java (Programming Language), Application Programming Interfaces (APIs), Amazon Web Services, Business Logic, Batch Processing, BigQuery, Data Deduplication, PostgreSQL, Machine Learning, MySQL, Node.Js, Query Optimization, Redis, Standard Sql, TypeScript, Backend, Kotlin, Data Analytics
- **Published:** September 26, 2026
- **Apply:** https://startup.jobs/senior-backend-engineer-ranking-systems-all-genders-about-you-se-co-kg-10195710

## About the Role

* 5+ years of experience with backend systems (Node.js/TypeScript preferred, but we welcome fast learners from Java, Go, or Kotlin)
 * Strong hands-on SQL knowledge (Postgres/MySQL schema design, query optimization, and batch operations beyond basic ORMs)
 * Good algorithmic intuition for sorted data, deduplication, latency trade-offs, and constraint logic
 * You're excited to bridge backend engineering and ML by serving model scores or ranking data in live systems
 * Clear communication skills in English and a pragmatic, solution-oriented mindset

Nice to Have

 * Experience with job queues (BullMQ, Redis) or batch processing pipelines
 * Exposure to cloud tooling (AWS Step Functions, CDK, GCP/BigQuery)
 * Background in e-commerce, sponsored products, or ad-tech systems
 * Curiosity about learning-to-rank algorithms

## Description

* Shape how millions of users see products by blending ML model outputs with business logic (like campaign boosts or sponsored items)
 * Build and own our high-throughput ranking engine ("Spotsetter") to ensure fast, deterministic, and fair product sorting
 * Design reliable batch write pipelines that stream data from BigQuery straight into high-performance relational stores like Postgres and MySQL
 * Develop low-latency serving APIs with Fastify and Node.js/TypeScript
 * Work closely with data engineers, product managers, and commercial teams to make data-driven ranking decisions
 * Architectural freedom: collaborate with our Tech Lead, bring in your own ideas, and keep our codebase clean, * You love digging into ranking problems, taking deep ownership of a product, and seeing your changes move real business metrics


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