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# Kotlin Backend SW Engineer

- **Company:** Hays
- **Location:** Barcelona, Spain (Remote available)
- **Salary:** €50,000.0
- **Contract:** Permanent contract
- **Skills:** Java (Programming Language), Application Programming Interfaces (APIs), BigQuery, Continuous Integration, Distributed Systems, Protocol Buffers, Java Virtual Machine (JVM), Python (Programming Language), PostgreSQL, MongoDB, NoSQL, Performance Tuning, SAP (Applications), TypeScript, Management of Software Versions, Openapi, Data Logging, Real Time Systems, Apigee, Backend, Kotlin, Kubernetes, Enterprise Integration, Apache Kafka, Api Gateway, Restful APIs, Terraform
- **Published:** October 28, 2026
- **Apply:** https://www.hays.es/detalles-vacante/kotlin-backend-sw-engineer-barcelona-and-4-days-home-office-per-week_1130785

## About the Role

* Strong experience building event-driven, distributed systems
 * Proficiency in Kotlin on the JVM; solid Java skills; familiarity with Python or TypeScript is a plus.
 * Proven track record designing contract-first RESTful APIs with OpenAPI, including versioning, error models, and API gateway policies (e.g., Kong/Apigee).
 * Practical experience with relational and noSQL databases (like MongoDB and PostgreSQL), schema design, transactions, performance tuning in high-throughput environments.
 * Experience in cloud-native operations, e.g. on GCP with Kubernetes and Terraform; GitOps (Flux), CI/CD, observability (logging, metrics, tracing), and production troubleshooting.
 * Integration expertise using synchronous and asynchronous patterns (Kafka, Google Pub/Sub, etc.) across enterprise systems
 * Strong focus on reliability, security, and compliance for customer order data (SLAs, auditability, PII/GDPR), with clear communication and cross-functional collaboration skills.

## Description

* Develop and maintain services for customer order processing, covering the end-to-end online order journey.
 * Build and manage APIs and integrations between the Order Management System and key corporate applications such as SAP, Checkout, Payments, Invoicing and Pick & Pack.
 * Orchestrate order workflows to ensure consistent and real-time processing across different systems.
 * Standardize order data and communication between multiple platforms and applications.

Your tasks

 * Design, implement, and evolve COS REST APIs and event schemas (OpenAPI, API Gateway), enabling contract-first integrations and decoupling consumers from Order Management platform.
 * Develop and orchestrate event-driven order workflows with Kafka/Kafka Streams and Temporal (basket-to-order, payment/checkout, digital activation, fulfillment, transport management), ensuring reliability, idem-potency, and auditability.
 * Build and maintain data persistence and propagation: model order data in Protobuf, MongoDB, PostgreSQL, drive real-time synchronization to corporate systems, and support analytics via Pub/Sub to BigQuery with strong data quality and PII safeguards.
 * Operate the platform on GCP/Kubernetes using GitOps (Flux): monitor and troubleshoot production, optimize performance and scalability, manage incidents, and continually improve SLAs, security, and resilience.