Senior Backend Engineer - Kotlin, Spring Boot

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Company Description

We Dream. We Do. We Deliver.
At Merkle, a dentsu company, we power the experience economy. Whether we’re building the next great app, running CRM at scale for global brands, delivering technology architectures that support millions of users, or providing world-class data, identity, and insights solutions, it’s all in the name of crafting experiences that set brands apart from the competition. Backed by dentsu's legacy of innovation and creativity originating in Japan, we’ve spent over 35 years helping brands build loyalty, drive growth, and connect meaningfully with their audiences. 
We’ve been named a global “Leader” by top industry analyst firms in categories as wide-ranging as digital transformation and commerce, experience design, engineering and technology integration, digital marketing, data science, CRM and loyalty, and customer data management.

About the role

We are looking for a Senior Backend Engineer to strengthen the service layer of an e-banking platform. You will design, build, and operate highly reliable, secure microservices written in Kotlin with Spring Boot, integrated via Apache Kafka event streams, and deployed on Red Hat OpenShift. Kotlin is a core requirement as you will work in close collaboration with the mobile engineering team. This is a hands-on role with broad scope: you will own services end-to-end from API contract design through to production observability, influence platform-wide architectural decisions, and act as a technical reference for your squad and the wider backend chapter.

Responsibilities:

• Design, develop, and maintain secure, scalable backend services and APIs using Kotlin and Spring Boot.
• Build and operate event-driven integrations via Apache Kafka including producers, consumers, Kafka Streams, and Avro schemas with exactly-once semantics.
• Own data models, query optimisation, and schema migrations across PostgreSQL and MySQL.
• Integrate services with observability, CI/CD, and DevOps tooling; support deployment and monitoring on OpenShift/Kubernetes.
• Apply security best practices in the realms of OAuth2/OIDC, authentication, authorisation, and encryption.
• Conduct code reviews, uphold engineering standards, and mentor junior engineers.
• Produce high-quality technical documentation covering design, implementation, and API contracts.

Required qualifications:

• 5+ years of professional backend engineering experience.
• Proficiency in Kotlin.
• Strong hands-on experience with Spring Boot (Spring MVC, Security, Data JPA, Cloud, Actuator).
• Solid Apache Kafka experience including Kafka Streams, Schema Registry, and exactly-once semantics.
• Proficiency with PostgreSQL and MySQL: data modelling, query plans, replication, and working with connection pools (HikariCP).
• Practical experience with Kubernetes or OpenShift.
• Sound understanding of distributed systems, microservices architecture, and design patterns.
• Familiarity with OAuth2/OIDC and backend security fundamentals.
• Proficiency with Git and CI/CD practices.
• German B2+, primary language for team communication, documentation, and stakeholder interaction.
• English business proficient, used for technical standards and international tooling.

Nice to have:

• Bachelor's degree in computer science, information technology, or equivalent experience.
• Prior experience in regulated industries such as banking or fintech.
• Familiarity with Spring Cloud and distributed tracing tools.
• Experience with database migration tooling such as Flyway or Liquibase.
• French or Italian, advantageous given the multilingual nature of the Swiss platform.

Benefits:

These are some of the things we offer: 

• 25 days of holidays 
• 2 volunteer days for charitable activities
• Mental Health: Benefit from 3 extra wellness days on top of your vacation days and a Mental Health 
• First Aider and Employee Assisstance program to support your well-being
• 40-hour week & overtime compensation 
• Flexible working hours model (flextime)
• Independent home office management 
• State-of-the-art, creative office space with ergonomically equipped workstations
• Pet friendly offices
• Full access to Dentsu Academy, on-site learning sessions, online language courses
• Learning Allowance: Receive 40 additional hours per year for personal and professional development, on top of statutory educational leave
• Corporate benefits platform
• Referral bonus program
• Workation possibility
• Team events: company parties, monthly breakfasts, aperos

*At dentsu, Diversity, Equity, and Inclusion (DEI) is central to our vision: "To be at the forefront of people-centered transformations that shape society."
We cherish the unique talents and perspectives of all individuals, welcoming applicants regardless of gender, gender identity, nationality, religion, ethnicity, cultural background, sexual orientation, age, physical or mental ability. By embracing diverse perspectives, we create meaningful change and sustainable growth for our people, clients, and society. Our hiring decisions are guided by qualifications and role-specific requirements, ensuring a workplace free from discrimination and harassment

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