Senior Backend Engineer - Ranking Systems

Location: Hamburg or Berlin, Germany

Salary: €70,000–€85,000 yearly

Company

hirify.global is a European e-commerce company combining fashion and technology to create personalized online shopping experiences.

What you will do

• Build and own the high-throughput ranking engine “Spotsetter” for fast, deterministic, and fair product sorting.
• Combine machine-learning model outputs with business logic, including campaign boosts and sponsored products.
• Design batch write pipelines streaming data from BigQuery into PostgreSQL and MySQL.
• 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.
• Contribute to architecture, code quality, and technical direction with the Tech Lead.

Requirements

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

Nice to have

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

Culture & Benefits

• Flat hierarchies, direct communication, and pragmatic decision-making.
• Ownership, trust, and clear responsibility with architectural freedom.
• Inclusive environment focused on acceptance and diverse perspectives.
• Team lunches, afterwork drinks, company events, and informal social interaction.
• Additional benefits are provided through the company benefits program.

Hiring process

• Apply online through the career page.
• The recruiting team will follow up after application review.