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-technical stakeholders
Passionate about development and eager to keep learning
What We Offer
Fully remote or hybrid — join the team in our Dublin 16 office whenever you like, or skip the long commute
Competitive salary, depending on experience
21 days' annual leave, plus an extra day for each complete year worked, up to 25 days per year
Summer Fridays — half days on Fridays throughout the summer
Pension scheme
Referral scheme
Maternity benefit
This is a fantastic opportunity to join a company that cares about its people, likes to promote talent from within, and is continually growing in new markets. If you don’t have all the requirements but this could be the right role for your career, apply for this position. We are looking for the best cultural fit.

Work arrangement
Yes