Senior Backend Engineer - Ranking Systems (all genders)

Description

The company is one of Europe's fastest-growing e-commerce businesses, operating where fashion meets technology.

Your work shapes which products millions of users see, by combining ML model scores with business rules such as campaign boosts and sponsored placements.

You will own the high-throughput internal ranking engine, which sorts products quickly, predictably and fairly.

Decisions are made directly, without long approval chains, and the company values ownership and clear responsibility.

Responsibilities

• Combine ML model outputs with business logic such as campaign boosts and sponsored items.
• Build and maintain the high-throughput ranking engine for fast, deterministic and fair product sorting.
• Design reliable batch pipelines that stream data from BigQuery into high-performance relational databases such as Postgres and MySQL.
• Build low-latency serving APIs with Fastify and Node.js/TypeScript.
• Work with data engineers, product managers and commercial teams on data-driven ranking decisions.
• Agree architecture with the Tech Lead, bring in your own ideas, and keep the codebase clean.

Requirements

• You enjoy digging into ranking problems, owning a product end to end, and seeing your changes move business metrics.
• 5+ years of backend experience, ideally with Node.js/TypeScript; fast learners coming from Java, Go or Kotlin are welcome.
• Strong SQL skills, including schema design, query tuning and batch operations in Postgres or MySQL beyond basic ORM use.
• Solid algorithmic thinking for sorted data, deduplication, latency trade-offs and constraint logic.
• Interest in bridging backend engineering and ML by serving model scores or ranking data in live systems.
• Clear communication in English and a pragmatic, solution-focused approach.
• Experience with job queues (BullMQ, Redis) or batch processing pipelines.
• Exposure to cloud tools such as AWS Step Functions, CDK or GCP/BigQuery.
• Background in e-commerce, sponsored products or ad-tech systems.
• Curiosity about learning-to-rank algorithms.

Conditions

Based in Hamburg and Berlin.

Everyone is welcome at the company, exactly as they are, regardless of background.

Benefits

• Perks are listed on the company's benefits page.
• Team lunches, after-work drinks, company events and quick coffees between meetings.