Java Backend Developer

Mercaux is an in-store B2B SaaS Platform that aims to transform offline retail and help traditional retailers smoothly transition into the digital era. Founded by Harvard Business School alumni and ex-Yandex tech team, Mercaux's products are live in 40 countries including the UK, Italy, Spain, US, Canada, and Thailand.

Currently, we are looking for a Middle+ Backend Developer to optimize our AWS services, boost scalability, and build a strong base for advanced analytics and machine learning, with a possible move to Azure.


At Mercaux, our backend is a collection of cloud-based RESTful API services built on the reliable Java (and a tiny bit of Kotlin) + Spring + Hibernate stack. One standout feature for us is our multi-tenancy approach, where all Mercaux clients coexist within a single infrastructure.

As a result, our backend needs to effectively manage data and permissions across users and roles, while maintaining ISO 27001 and PCI compliance. These services play a crucial role in our ETL system and are utilised by our iOS, Android, and Web applications.

From a business perspective, these services handle user authentication, rights management, data storage and retrieval, message forwarding through the Twilio API, integration with OMS, and much more. We're seeking a skilled backend developer who can help scale out our platform's core (e.g., preparing for potential sharding) and drive the development of new business scenarios.

What you will need to do

• Developing and maintaining a suite of AWS-based services (with potential expansion to Azure in the future).
• Enhancing scalability and identifying performance bottlenecks.
• Building the foundation for advanced analytics using statistical and machine learning techniques.
• Collaborating closely on optimising memory and CPU utilisation, as well as fine-tuning complex SQL queries.

How to know if you are the right fit

• You've worked with similar infrastructure: Linux, PostgreSQL, AWS (SQS, SNS, S3, CloudFront).
• You possess solid Java skills: Hibernate, Spring, Spring Boot.
• You're well-versed in SQL: optimising complex queries, memory and CPU usage, etc.
• You're experienced with development tools: CI/CD deployment (TeamCity), Bash, GitFlow.
• You have familiarity or hands-on experience with: AWS ECS, EC2, ASG, RDS, Lambda, Docker, Load testing (JMeter).
• You can effectively communicate in English for work purposes, especially in written form.
• You're hands-on, take full ownership of your work, and value accountability from start to finish.

We offer

• Remote worldwide or hybrid workplace (with the office in Barcelona or Serbia).
• Competitive salary.
• Health Insurance (upon probation).
• Paid time-off + applicable local public holidays.
• International, diverse, and dynamic team.
• Opportunity to create something new, and to transform the retail industry.