Senior Backend Java/Kotlin Engineer E-commerce (Poland / Remote)

We are open to hiring people from Ukraine.

We're inviting you to work together on a tool that will help customers worldwide manage their money with zero effort. Join the ZEN.COM team now and change the world of finance for the better. At ZEN.COM, you will get to work with many exciting new technologies.

TL;DR checklist:

• 4+ years working on e-commerce projects (marketplaces, logistics, shopping, etc.)
• Understanding of challenges around e-commerce processes
• Open to experimenting with AI
• Experience building large service-oriented systems and complex processes
• Fluent in Spring and Java/Kotlin
• Experience designing and consuming REST APIs
• Comfortable with remote-first work

All checked? In that case, send us your CV! And if you want more details, read on.

The Opportunity

Help us design and build an ambitious e-commerce system that helps customers find the right product at the best price. Together, we’ll create solutions that take the complexity out of online shopping and streamline the process, while always keeping the user’s best interest at the center. This is a unique opportunity to work on software that is truly user-focused — built to support people, not manipulate them. We operate with a startup mindset: a small, senior, fast-moving team. We’re energetic, collaborative, and pragmatic. We use AI at multiple layers of the product — you’ll both use and shape these production-ready applications and learn a lot along the way.

Requirements

Your work becomes the backbone of pricing & availability intelligence used across products and markets

• Learning: Hands-on work with production AI (LLMs, embeddings, agents) and modern data engineering
• Team: Talented, supportive peers; high autonomy and ownership; clear problem statements
• Pace & pragmatism: We ship, measure, and improve

Responsibilities

• Build components of a service-oriented ecosystem using a mix of synchronous and asynchronous communication
• Design processes that support and connect key parts of the system
• Work on AI agents and AI flows that automate data gathering, matching, and processing
• Actively participate in workshops on domain design (e.g. event storming), business processes, and UI design (in close collaboration with our UX team)
• Develop flexible search solutions by combining full-text search, vector search, and graph databases
• Build rich knowledge bases that serve as the backbone for our system

What you bring:

• Deep understanding of the e-commerce domain and its processes, from both the customer and merchant perspective
• Expertise in Spring and Java/Kotlin; confidence in building RESTful services and event-driven systems
• Strong grasp of good code design principles and testing practices
• An open mind for unconventional and creative solutions
• Ability to design flexible systems that can support business pivots
• Understanding of performance factors and how to ensure a fast, responsive experience for the user

What We Offer

• 4+ years working on e-commerce projects
• Understanding of challenges around e-commerce processes
• Fluent in Spring and Java/Kotlin

Nice to have:

• Experience with AI — both in the systems you build and in the tools you use
• Understanding of NoSQL / modern data stores such as MongoDB, Elasticsearch, Neo4j, or BigQuery
• Background in building or maintaining high-traffic systems
• Understanding of e-commerce at a global scale (across countries and continents)
• Knowledge of Python 3.12+