Backend Engineer - Ranking Systems

Bertelsmann SE & Co. KGaA
Hamburg, Germany
1 day ago
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Role details

Contract type
Permanent contract
Employment type
Full-time (> 32 hours)
Experience level
Expert
Experience required
5 years minimum
Working hours
Regular working hours
Languages
English
Job source

Tech stack

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
+6 more
Redis Standard Sql TypeScript Backend Kotlin Data Analytics

Job 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 (ā€œSpotsetterā€) 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

Requirements

  • 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

Benefits & conditions

Different backgrounds and perspectives make us stronger and shape our culture in ways that matter.

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Good distractions

Talks and stories from around this role — technically off-topic, practically not.

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Understanding Kotlin Multiplatform and its compiler targets

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Transitioning into backend engineering from web development

Stefan Lingler Stefan Lingler +1 Ā· Coffee With Developers

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Comparing in-memory and Redis storage for cache scalability

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