Expert Java Developer

Incluso AB; Stockholms kommun; On-site; SEK 520,000 - 720,000; Full time

Job summary

Incluso AB in Stockholm is seeking an Expert Java Developer to design and implement backend services for customer migration programs. You will build REST APIs, batch processing, and routing logic, while guiding architectural decisions and ensuring scalable, observable systems.

The role is onsite in Stockholm with a Sep 2026 start and a 9-month contract with potential extension. The ideal candidate brings deep Java 10+ experience, Spring ecosystem expertise, and strong communication skills in

Qualifications

• Proven experience delivering Java/Spring microservices at scale.
• Strong architectural capabilities and leadership in tech decisions.
• Fluency in Swedish and English is required.

Responsibilities

• Design and develop Java/Spring Boot REST APIs to determine customer stack and routing decisions.
• Build identification mechanisms and batch processing for migrations and stacks.
• Create services for tracking migrations and statuses and expose APIs for UI.
• Ensure high availability, security, and observability with logging and monitoring.
• Collaborate with frontend, architects, DevOps, and migration teams.

Skills

Java 10+

Spring Boot

REST APIs

Microservices

Spring Data JPA/Hibernate

SQL

Spring Batch

Lookup/Routing services

OAuth 2.0 / OpenID Connect / JWT

JUnit/Mockito/Testcontainers

Maven/Gradle

Git/CI/CD

Docker

Kubernetes

Architecture design

Logging/Observability

Swedish and English fluency

Job description

We are looking for an Expert Java Developer for a global company in Stockholm.

Start is in Sep 2026, 9-months limited contract to begin with, possibility of extension after that.

We are looking for an experienced Java Developer with strong architectural capabilities to design and implement backend services supporting customer identification, stack determination, migration tracking, and application routing during a customer migration program. The role should also provide strategic technical direction and guide the team in architectural decisions.

Key Responsibilities

• Design and develop Java/Spring Boot REST APIs to determine the appropriate customer stack based on Customer ID and other stack-related identifiers.
• Build flexible identification mechanisms that can be extended with additional identifiers as business and migration requirements evolve.
• Implement batch processing solutions for loading, updating, and maintaining customer migration and stack information.
• Develop services for tracking which customers and associated identifiers have migrated and their current migration/stack status.
• Provide backend APIs supporting Customer Identification UI functionality.
• Enable UI/application redirection based on customer identification, stack assignment, and migration status.
• Expose customer stack and migration status to frontend applications where required.
• Implement routing and lookup capabilities supporting customers throughout the migration window, including transitional states while migration is in progress.
• Design dedicated migration-status and stack-lookup services/APIs where appropriate.
• Ensure APIs are highly available, secure, scalable, observable, and resilient.
• Implement appropriate caching, validation, error handling, logging, monitoring, and auditability.
• Create automated unit, integration, and API tests and contribute to CI/CD pipelines.
• Provide strategic architectural direction to the team, translate long-term objectives into pragmatic technical decisions, and ensure alignment across services, integrations, data flows, and migration patterns.
• Collaborate closely with frontend developers, architects, DevOps engineers, product owners, and migration teams.
• Be a collaborative team player who actively shares knowledge, supports colleagues, and contributes to shared team success.

Required Technical Skills

• Strong experience with Java 10+
• Strong experience with Spring Boot and Spring Framework
• REST API and microservice design
• Spring Data JPA / Hibernate
• SQL and relational databases
• Batch processing, preferably Spring Batch
• Experience designing lookup and routing services
• API security using OAuth 2.0 / OpenID Connect / JWT
• Unit and integration testing using JUnit, Mockito, Testcontainers, or equivalent
• Maven or Gradle
• Git and CI/CD
• Docker and containerized applications
• Kubernetes and cloud-native deployment
• Strong architectural knowledge, including the ability to define target architecture, evaluate trade-offs, establish design principles, and guide the team in complex architectural matters
• Logging, monitoring, metrics, and distributed tracing
• Fluency in Swedish and English is required.

Desirable Experience

• Experience with large-scale customer or platform migrations
• Designing systems that support old and new application stacks simultaneously
• Customer identity/identifier mapping and resolution
• Migration-state management such as NOT_MIGRATED, MIGRATION_IN_PROGRESS, MIGRATED, and failure/rollback scenarios
• Event-driven architecture and messaging technologies such as Kafka
• Redis or similar caching technologies
• Azure/AWS cloud platforms
• API gateways and traffic-routing solutions
• High-volume batch data processing and reconciliation

Key Engineering Competencies

The ideal developer should be comfortable designing services where a request such as:

Customer ID → Customer Identification → Stack/Migration Lookup → Routing Decision → Target Application

can be performed reliably and with low latency.

Particular emphasis should be placed on extensibility, since customer identification may initially use Customer ID but needs to support additional identifiers in the future, and on migration safety, because routing decisions must remain accurate while customers transition between stacks.

Beyond hands-on development, the ideal candidate can act as an architectural sounding board for the team, create clarity in technically complex areas, and set a coherent strategic direction that supports both immediate delivery and long-term maintainability.

This is a full-time consultant position in Stockholm through Incluso. Start is in Sep 2026, 9 months limited contract to begin with. This role is 100% onsite in Stockholm.