Junior Data Engineer (all genders)

We are looking for a curious and driven Junior Data Engineer to join our BI team. In this role, you will design and maintain data pipelines on AWS, support our analytical infrastructure, and contribute directly to making Cardmarket's data systems faster, more reliable, and more cost-efficient. This is not a passive reporting role. You will actively shape how data flows through our cloud architecture - with a strong emphasis on AWS S3 as our data lake, and pipeline engineering as your primary focus.

Tech Stack You will work with the following technologies on a daily basis:

• AWS S3
• AWS Glue / Lambda
• Python
• SQL
• Microsoft Fabric
• Power BI
• GitLab
• Jira

Your Responsibilities

Cloud & Pipeline Engineering (AWS - Core Focus)

• Design, build, and maintain scalable data pipelines on AWS, with a strong emphasis on optimizing both computational performance and cloud cost efficiency.
• Work extensively with AWS S3 as the primary data lake: define partitioning strategies, select appropriate file formats (Parquet, Delta, JSON), and enforce data organization best practices.
• Leverage AWS-native services (Glue, Lambda, Step Functions, Athena, CloudWatch) to automate ingestion, transformation, and delivery workflows.
• Monitor pipeline performance, identify bottlenecks, and implement architectural improvements that reduce processing time and AWS spend.
• Apply cost-optimization principles: right-sizing compute resources, minimizing redundant data reads, leveraging S3 storage tiers, and avoiding unnecessary full-table scans.
• Implement automated data quality checks, validation rules, and alerting to ensure pipeline reliability and data consistency.

Data Engineering & BI Support

• Extract, transform, and load (ETL) data from multiple sources into our BI systems using SQL and Python.
• Clean and prepare raw data for analysis, ensuring quality, consistency, and readiness for downstream consumption.
• Build and maintain datasets and semantic models in Microsoft Fabric to support reporting layers.
• Develop and maintain dashboards and reports in Power BI for stakeholders across departments.
• Monitor key marketplace KPIs and surface proactive insights on trends, anomalies, and opportunities.

Collaboration & Process

• Collaborate with Marketing, Product, and Operations teams to understand data requirements and deliver actionable solutions.
• Maintain clean, well-documented, version-controlled code in GitLab following team standards.
• Manage tasks and priorities transparently via Jira within agile workflows.
• Conduct ad hoc analyses and provide data-driven recommendations to support business decision-making.
• Stay up to date with AWS services, data engineering patterns, and BI trends - and bring learnings back to the team.

Do you have experience in SQL?, Do you have a Bachelor's degree?, * Bachelor's degree in Computer Science, Data Science, Engineering, Statistics, or a related field.

• Solid SQL skills - including complex joins, aggregations, window functions, subqueries, and query optimization.
• Hands-on experience or strong foundational knowledge of AWS S3: partitioning, file formats, access patterns, and lifecycle policies.
• Familiarity with ETL concepts: data pipeline architecture, transformation layers, batch processing, and data quality practices.
• Basic Python proficiency for data manipulation and pipeline automation (pandas, boto3, or similar).
• Understanding of cloud resource and cost optimization principles - e.g., columnar formats, compression strategies, compute right-sizing.
• Experience with Git / GitLab for version control and collaborative development.
• Strong analytical mindset with the ability to detect and investigate data anomalies.
• Excellent written and verbal communication in English; able to present technical findings to non-technical audiences.
• Fluent English skills
• Presence in Berlin is required
• Valid Work Permit for Germany is preferable

Nice to Have

• AWS Services: Hands-on experience with AWS Glue, Lambda, Step Functions, Athena, or CloudWatch for data workflows.
• Microsoft Fabric: Familiarity with Microsoft Fabric, Lakehouses, Dataflows Gen2, or Synapse Analytics.
• Power BI / DAX: Experience building reports and dashboards in Power BI, including basic DAX measures and calculated columns.
• Pipeline Optimization: Documented experience reducing pipeline runtime or cloud costs through architectural decisions.
• Marketplace Analytics: Familiarity with e-commerce or marketplace KPIs: conversion rates, GMV, seller performance, user acquisition.
• Agile: Practical experience working with Jira in a team or project setting.

Cardmarket is all about the people. Our goal is that all people in the company come inspired to work, feel safe at work and return fulfilled at home. The most important part of our corporate culture is open communication, because only when we talk about problems, no matter how big or small, can we find a solution together. Cardmarket connects people from all continents of the world, regardless of race, colour, ancestry, religion, national origin, gender or sexual orientation. We treat all people in the same way and we expect the same from all our applicants. It is the different perspectives that makes us stron as a Cardmarket Family and make us ready to go into the future together as a diverse and inclusive team., Your everyday work You will work in a full-time position (39 hours per week) at our office in Berlin Prenzlauer Berg - a place where creative energy, exchange, and focus come together. At the same time, we offer a hybrid working model and provide you with all the equipment you need for your work. Thanks to flexible working hours with clearly defined core hours, you can structure your day in a way that allows work and private life to harmonize well. * Community & Culture We meet each other as equals. An informal, first-name culture is a given - from interns to management. We believe that great results are achieved where people feel seen, heard, and valued. Our shared passion for trading card games connects us - at work and beyond. It symbolizes what defines us: curiosity, strategy, teamwork, and the drive to continuously challenge ourselves. * Vacation & further benefits Five weeks of paid vacation as well as a Germany-wide public transport ticket (Deutschlandticket) that supports you flexibly in your everyday life. A lunch allowance (up to €7.67 per working day) as well as free drinks and snacks are also part of our benefits. * Your development matters Standing still is not an option for us - at least not in a positive sense. With a personal annual learning budget of €1,500, we deliberately invest in your development: conferences, courses, books, or new skills - you decide what helps you move forward. * Mental & physical health We know: Great performance can only happen when people are doing well. That's why we support you with an Urban Sports Club membership for your physical balance, our collaboration with DearEmployee, which offers anonymous, professional psychological support, and the Women of Cardmarket & LGBTQIA+ Group, which promotes exchange, visibility, and empowerment. * In short With us, you won't find anonymous open-plan offices or rigid structures, but a work environment with heart, values, and genuine appreciation - a place where you're not only allowed to be yourself, but expected to be, take responsibility, and continue developing, professionally and especially personally.