Middle/Senior Backend Developer

We are looking for a Senior BackEnd developer (in Barcelona, Serbia, or remote) 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. Check out more details about our architecture here.

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’re 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
  

What we offer:

• International, diverse, and dynamic team
• Opportunity to create something new, and to transform the retail industry
• Learning & Development Allowance (upon probation)
• Competitive salary & Bonus scheme (subject to performance)
• Health Insurance (upon probation)
• Opportunity to participate in the Options scheme (upon probation)
• Paid time-off + applicable local public holidays
• Trips to Mercaux offices
• Relocation allowance + legal support (if relevant; upon probation)
• Hybrid workplace (with the office in Barcelona or Serbia)