Senior Backend Developer (Java / Spring Boot)

[Ireland or Remote in EU]

Sim Local is a leading global travel eSIM provider, helping millions of travellers stay connected in over 200 destinations worldwide. Through a combination of local operator partnerships, innovative digital products, and omnichannel distribution, we deliver seamless connectivity experiences for international travellers.

We’re looking for a Senior Backend Developer with a strong track record of delivering production services and APIs end to end. You’ll own backend services and API implementation across our multi-tenant, multi-brand eSIM and travel SIM platform, with real influence over architecture and technical decisions.

Your work will power our D2C website and mobile app, our white-label partner stores, our internal platform, and the Networks and payment integrations behind them.

Our stack: Java 17+, Spring Boot, Maven, MySQL, JPA/Hibernate, Liquibase and AWS (SQS/SNS, Lambda, Cognito, SES, CloudFormation).

Key Responsibilities

1. Backend Services & APIs

• Design, build and ship backend services and APIs across our platform — customer-facing APIs, internal back-office systems, and partner integrations
• Build, maintain and scale our Java / Spring Boot services and API gateways, keeping them secure and reliable in production

2. Third-Party Integrations

• Build and maintain integrations with networks, payment or 3rd party providers, including webhooks and event-driven flows
• Design for failure — idempotency, retries and graceful handling of errors across distributed systems

3. Architecture, Code Quality, Incident management

• Contribute to architecture decisions and help shape the technical direction of the platform as it scales
• Identify and resolve performance bottlenecks and security vulnerabilities before they reach production
• Review code — including AI-generated code — and raise the bar for quality, testability and security across the team
• Champion automated testing, clear API documentation and good engineering habits
• Own the services you build in production, using observability and monitoring to keep them fast, efficient and secure at scale
• Partner with platform engineering on infrastructure, deployments and incident resolution

4. Team Collaboration

• Work with the Product Owner, developers and technical leaders to deliver focused, value-driven changes to the highest standard
• Contribute to planning, agile ceremonies and continuous improvement of how the team works

What We’re Looking For

Essential – All Candidates

• Bachelor’s degree in computer science or other relevant discipline or equivalent work experience.
• 4+ years of backend development experience, with a proven track record of delivering production services end to end
• 2+ years experience building RESTful APIs and web services.
• Strong Java (17+) and Spring Boot, including Spring Security / OAuth2 and multi-module Maven projects
• Relational databases (MySQL or similar), JPA/Hibernate and schema migration tools such as Liquibase — including schema design and query optimisation at scale
• Cloud-native services on AWS — SQS/SNS, Lambda, Cognito, SES, and CloudFormation or similar infrastructure-as-code
• Asynchronous, message- and event-driven architectures, including distributed systems patterns such as idempotency and retry handling
• Automated testing — unit testing with JUnit and Mockito, and integration testing with Testcontainers or equivalent
• Observability and monitoring with APM tooling (Datadog, New Relic, CloudWatch or similar)
• Hands-on use of Claude Code or similar AI coding assistants, with the judgement to review, correct and take full ownership of AI-generated code
• Strong code review skills and a track record of raising the bar for code quality across a team
• Caching strategies and high-traffic, high-concurrency systems (e.g. Redis)
• Integrating third-party APIs and webhooks — payment providers, telecom/carrier providers, or CRM/marketing platforms
• Experience in a cross-functional Scrum team using Jira and Confluence

Desirable

• API documentation with OpenAPI / Swagger
• Background in telecom, eSIM, travel or e-commerce

Personal Qualities

• Strong delivery focus — takes ownership from design through to production
• Proactive — spots improvements and feels empowered to drive them
• Maintains and defends high engineering standards with good practices and habits
• Collaborative, clear communicator with product and non-tech…