Senior/ Middle Level Backend Developer

**Company & Product**
Mercaux's In-Store Clienteling and CX Unified Commerce Platform empowers retailers to deliver exceptional shopping experiences, both in-store and remotely, to boost sales, loyalty, and profitability
A single app for Store Associates offers assisted selling, endless aisle, clienteling & appointments management, through to in-store interest capture, remote selling, mPOS, Intelligent Task Management, Store Associate performance Dashboards, fulfillment & returns. Self-service customer solutions include progressive web apps, digital fitting rooms, self-checkout kiosks, and appointment bookings.
The MACH-certified modular platform allows for flexible transformation at the retailer's pace - start with assisted selling or clienteling, or deploy digital fitting rooms.
Additional solutions, such as self-checkout and remote selling, can be easily added at a later date.
Mercaux has an international team spread across London and Barcelona offices with some employees working remotely.
**Who we are looking for and why**:
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.
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)
- 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)

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