Java runs the core systems of financial services, logistics, healthcare, and enterprise commerce. When those systems need building, extending, or modernising, they need developers who understand the JVM, the Spring ecosystem, and production-grade Java. KiwiCommerce supplies UK-based Java developers for Spring Boot APIs, enterprise backends, microservices, and legacy Java modernisation. 250+ projects delivered since 2016.
Most Java APIs can be made to work. Fewer are built to survive production at scale. Our developers write Spring Boot applications with the layering, test coverage, and security configuration that keep them maintainable as systems grow and teams change.
Get In TouchController, service, and repository separation is not optional on our builds. Neither is DTO mapping, exception handling, or OpenAPI documentation.
Java 25 LTS (September 2025) and Java 21 LTS are our production targets. We do not build on non-LTS releases and we advise on version risk from the first conversation.
Spring Boot 3.x and 4.x require the javax-to-jakarta namespace migration. Our developers know the breaking points and manage the full upgrade path.
Unit tests with JUnit 5 and Mockito, integration tests with Spring Boot Test, and coverage reporting via JaCoCo are written alongside the code, not after.
Enterprise Java projects fail less often because of bad language choice and more often because of bad implementation decisions. Spring Boot is fast to start with and slow to fix when the architecture is wrong. Services grow into monoliths. Tests are skipped. Security is bolted on. The JVM is blamed for problems that are actually N+1 queries in Hibernate.
Our Java developers work at both layers: the Spring framework layer and the core Java layer underneath it. They know the Spring Security filter chain, the JPA lifecycle, the Spring Cloud service discovery patterns, and the JVM performance characteristics that affect real production systems. That depth is what separates a Spring Boot application that holds up from one that needs rearchitecting six months after go-live.
For greenfield Java builds, we define the architecture, data model, and API contract before writing code. For legacy Java modernisation work, we read the existing codebase first, document what is there, and plan the migration to Java 21 or Java 25 LTS in stages. For dedicated Java developer retainers, the same developer works on the same application consistently, building the codebase knowledge that makes good decisions fast.
KiwiCommerce has been delivering backend systems and eCommerce platforms since 2016. An NDA is signed on every engagement. UK-based team working your hours. Speak to us about your Java project today.
Discuss Your Project2+ Experience Years
Works on clearly specified features in an existing Spring Boot codebase under senior oversight. Understands core Java, JPA repository queries, and unit testing with JUnit 5 and Mockito. Builds cleanly within an established project structure on well-defined tasks. Not suited for architecture decisions or JVM performance work without close guidance.
5+ Experience Years
Owns complete Spring Boot features end-to-end: JPA entity design, service layer logic, REST controller, and test coverage. Proficient in Spring Security, Hibernate query optimisation, Maven or Gradle, and Docker containerisation. Makes sound decisions on exception handling strategy, database query efficiency, and REST API design. Works independently on mid-complexity Java web developer projects.
7+ Experience Years
Architects' Spring Boot applications and microservices for long-term stability. Deep knowledge of the Spring ecosystem, JVM performance and garbage collection tuning, distributed system patterns, Kafka and RabbitMQ, Docker and Kubernetes deployment, and testing strategy at scale. Makes the decisions that determine whether a Java system scales cleanly or needs costly rearchitecting eighteen months later.
5+ Experience Years
Specialist in the Java language rather than primarily in frameworks. Deep understanding of Java concurrency and threading, the Collections framework, generic type system, stream processing, JVM memory model, and newer language features: records, sealed classes, pattern matching, and virtual threads from Project Loom. Best suited for high-throughput backend components, libraries, and performance-critical application logic.
5+ Experience Years
Assigned consistently to your application on a retainer basis, building institutional knowledge of the codebase rather than starting from scratch on each piece of work. Makes most sense for Java applications with an ongoing development backlog: enterprise backends, live Java web applications, or a Java API serving a React or Angular frontend.
4+ Mixed levels
An experienced Java developer working as a committed resource on your project remotely, at UK working hours. The same developer on the same codebase, with full accountability and transparent progress tracking. All code in version control, all deliverables documented. For organisations that need senior-level dedicated Java coverage without a permanent headcount addition.
What You Get When You Hire Java Developers
Properly layered Spring Boot REST APIs with controller, service, and repository separation. DTO mapping, Spring Security JWT and OAuth2 authentication, Bean Validation, exception handling, and OpenAPI documentation included as standard, not added on request.
Modular Java microservices using Spring Cloud for service discovery, API gateway, distributed configuration, circuit breaking, and distributed tracing with OpenTelemetry. Each service independently deployable, each with its own data store where appropriate.
Full Spring MVC web applications, server-side Java with Thymeleaf or serving a React or Angular frontend, with proper transaction management, Spring Security, and caching. Built for multi-developer teams, maintaining them across years of change.
Database integration using Hibernate ORM or Spring Data JPA with PostgreSQL, MySQL, or Oracle. Entity relationship mapping, lazy loading configuration, query optimisation, and database migration management with Flyway or Liquibase.
Migrating Java 8 and Java 11 applications to Java 17, 21, or 25 LTS. Updating to Spring Boot 3.x or 4.x, migrating from javax to jakarta namespaces, resolving dependency conflicts, and adding test coverage to validate behaviour before and after migration.
Containerising Spring Boot applications with Docker and deploying to Kubernetes on AWS EKS, GCP GKE, or Azure AKS. Health checks, readiness probes, autoscaling, and CI/CD pipeline configuration for production Java workloads
Spring Boot makes it easy to start a Java application. Making it maintainable, testable, and secure at production scale takes a different level of discipline. Here is what we bring to Java projects that most agencies do not.
Many Spring Boot developers know how to use Spring. Fewer understand why it behaves the way it does under production load, what happens when JVM garbage collection pauses affect response times, or how to read a thread dump and resolve a deadlock. Our senior Java developers work at that depth. That is the difference between a Java application that performs and one that gets blamed for being slow.
Every Java developer on your project is UK-based. Sprint reviews, architecture decisions, and production issues get addressed within the working day, not at the start of the next. For enterprise Java systems where architecture decisions carry long-term consequences, having your developer reachable in real time is not a preference. It is a practical requirement.
Java 26 (March 2026) has six months of support. Java 25 LTS (September 2025) and Java 21 LTS are the production targets. We build on supported LTS versions and advise clearly on upgrade timelines for existing applications. Java 8 and Java 11 systems carry real security and maintenance risk. We say so, and we fix it.
Spring Boot 4.0 and Spring Framework 7.0 (November 2025) are significant steps forward from earlier Spring generations. Our developers work with the current stack: Jakarta EE 11, Spring Security 6.x, Spring Data, Spring Cloud, and the full suite. That knowledge is the difference between a Spring Boot application that benefits from modern Java performance improvements and one that is locked out of them.
NDA signed on every engagement. Your application code, API design, business logic, and data remain private throughout. At project close, full technical documentation is produced covering architecture, data model, API contracts, and deployment configuration. A future developer inherits a codebase they can work in, not a black box they have to decode.
A single dedicated Java developer for an ongoing retainer. A Java development team for a microservices build or legacy modernisation programme. A senior Java architect for a design and review phase. We structure the engagement around what your Java project actually demands, not around a single model we apply to every client.
KIWI Commerce redeveloped my entire website, exactly to my requirements. They worked exactly along with my timeframe and were fantastic to work with. I would highly recommend this company. Thank you Sam and the team!
Great response to tickets. We feel our website is in safe hands with Kiwi. Any issues are fixed very quickly. Great value for money. We have been working with Kiwi for a couple of years now and find them very helpful and easy to get along with. Would highly recommend.
Working with Kiwi Commerce has been a very smooth experience. Their team is responsive, knowledgeable, and always willing to go the extra mile. From development to ongoing support, everything is handled efficiently and with great attention to detail. Highly recommended.
We’ve been working with Kiwi Commerce for ongoing website improvements and support, and the experience has been consistently positive. They are proactive, easy to work with, and quick to respond whenever we need assistance. Great team and great service.
Your questions answered.
Cannot find what you are looking for? Contact our team.
A Java developer builds and maintains server-side applications, APIs, and backend systems using the Java programming language. Most enterprise Java work involves the Spring Boot framework for REST API and web application development, Spring Data JPA and Hibernate for database integration, and Spring Security for authentication. Senior Java developers also handle JVM performance tuning, architecture design, and microservices patterns using Spring Cloud.
Core Java is the language and standard library: OOP principles, the Collections and Streams APIs, concurrency, the memory model, and newer features like records and virtual threads. Spring Boot is a framework built on top of core Java that adds structure for web application and API development, dependency injection, database integration, and security. Enterprise Java work requires both. A developer who knows Spring Boot but has shallow core Java knowledge struggles on performance problems and complex design challenges.
Java 25 LTS (released September 2025) is the current recommended production version for new applications. Java 21 LTS remains widely used and is actively supported. Java 17 LTS is the minimum for Spring Boot 3.x and Spring Framework 6.x. Java 26 (March 2026) is a non-LTS release with six months of support, not for production. Applications on Java 8 or Java 11 carry increasing security and maintenance risk and should be migrated to Java 21 or Java 25 LTS as a priority.
Yes. Legacy Java modernisation is one of the more technically demanding Java development tasks when done correctly. Our senior Java developers read and understand the existing codebase before changing it, document what is currently running, plan a staged migration to Java 17, 21, or 25 LTS that preserves application behaviour, and add test coverage to validate that behaviour throughout the upgrade. For Spring Boot 2.x to 3.x or 4.x upgrades, we manage the full javax-to-jakarta namespace migration and dependency compatibility resolution.
Both. For ongoing Java development on a specific application, a dedicated Java developer works on the codebase consistently on a monthly retainer — building the context needed to make good decisions at pace rather than re-learning the system on every task. For larger Java builds or modernisation programmes requiring multiple developers, we provide and coordinate Java development teams. We match the structure to what the project actually requires.
All of our Java developers are UK-based and work remotely as standard. We use Git for version control, a staging environment for testing before production deployments, an agreed sprint or milestone structure for project-based work, and regular progress check-ins. For dedicated Java developer retainers, we agree the communication cadence, tooling, and delivery tracking process before work begins so that progress is always visible and nothing sits in a black box.
Spring Boot is the most widely used Java framework for building REST APIs, microservices, and web applications. It provides opinionated defaults that remove boilerplate configuration, allowing developers to focus on application logic. Spring Boot 4.0 (supporting Java 25 LTS) and Spring Framework 7.0 (released November 2025) are the current production versions. Spring Boot simplifies database integration via Spring Data JPA, authentication via Spring Security, and cloud deployment, while remaining fully customisable for complex enterprise requirements.
Once we have reviewed your brief, assessed the existing codebase where relevant, and agreed the engagement model, a Java developer can typically start within one to two weeks. For dedicated Java developer retainers, the process covers a codebase review, developer matching, and agreement on the working arrangement before the retainer begins. Get in touch with your project details and we will give you a realistic timeline based on what the work actually requires.
Our UK-based Java development team is ready to look at your project. Whether you need a dedicated Java developer on a monthly retainer, a remote dedicated Java developer for ongoing work, a Spring Boot development team for a new API or microservices build, or expert Java developers to modernise a legacy Java 8 or Java 11 system, get in touch today. We respond within one business day.
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