Senior Backend Engineer (Sorting)

Location: Hamburg or Berlin, Germany

Salary: €70,000–€85,000 gross yearly

Company

European e-commerce company combining fashion and technology to create personalized and seamless online shopping experiences.

What you will do

• Build and own the high-throughput product ranking engine, combining machine-learning model outputs with business logic such as campaign boosts and sponsored items.
• Develop fast, deterministic, and fair product sorting for millions of users.
• Design batch write pipelines streaming data from BigQuery into high-performance relational stores.
• Develop low-latency serving APIs with Fastify and Node.js/TypeScript.
• Collaborate with data engineers, product managers, and commercial teams on data-driven ranking decisions.
• Work with the Tech Lead on architecture and maintain a clean codebase.

Requirements

• 5+ years of experience with backend systems.
• Professional experience with Node.js and TypeScript, or strong backend experience with Java, Go, or Kotlin.
• Strong SQL skills, including Postgres/MySQL schema design, query optimization, and batch operations beyond basic ORMs.
• Good algorithmic understanding of sorted data, deduplication, latency trade-offs, and constraint logic.
• Experience or interest in serving machine-learning scores or ranking data in live systems.
• Clear communication skills in English are required.

Nice to have

• Experience with BullMQ, Redis, job queues, or batch-processing pipelines.
• Experience with AWS Step Functions, CDK, GCP, or BigQuery.
• Background in e-commerce, sponsored products, or ad-tech systems.
• Interest in learning-to-rank algorithms.

Culture & Benefits

• Flat hierarchies, direct communication, pragmatic decisions, and clear ownership.
• Freedom to contribute architectural ideas and work closely with the Tech Lead.
• Inclusive environment that values different backgrounds and perspectives.
• Team lunches, after-work drinks, company events, and informal opportunities to connect.
• Additional benefits are provided through the company benefits program.

Hiring process

• Apply online through the career page.
• The hiring team will respond after reviewing the application.