Expertise
Java expertise: robust backends built to last
Java is a proven language and platform for systems that must run for years, under load, with changing teams. Java 21 LTS brings virtual threads, record patterns and pattern matching, which make code more concise and concurrency far simpler to write.
Agencei uses Java for enterprise backends: critical APIs, business rule engines, batch processing, integrations with ERPs or banking systems. We work mainly with Spring Boot, and with Quarkus when startup time matters.
This expertise is for organisations that need a stable, typed, well-tooled foundation that is easy to audit, or that must modernise an ageing Java application without rewriting it from scratch.
Use cases
Enterprise APIs
REST or gRPC services exposing sensitive business data, with OAuth2 authentication, audit logging and versioned OpenAPI contracts.
Batch processing
Nightly processing chains (billing, reconciliation, regulatory exports) with Spring Batch, error recovery and monitoring.
System integration
Connectors to ERPs, PIMs, payment or messaging systems (Kafka, RabbitMQ), with replay handling and idempotency.
Legacy application modernisation
Migrating Java 8 or 11 to Java 21, moving from Java EE to Jakarta EE or Spring Boot 3, containerising and adding tests.
Custom business software
Complex management applications (insurance, logistics, education) where rules evolve and must remain readable in the code.
Project types
- Enterprise REST or gRPC API
- Business management application
- Batch processing and reporting
- ERP or banking connector
- Java 8 to Java 21 migration
- Event-driven microservices
Integration with the rest of the stack
Java + Spring Boot + PostgreSQL
The most common combination on our projects: Spring Data JPA or jOOQ for data access, Flyway for schema migrations.
Java + Kafka or RabbitMQ
Event-driven architectures to decouple services, absorb peaks and replay messages after an incident.
Java + Docker + Kubernetes
Optimised images (Jib, layered jars, possibly GraalVM native), health probes and horizontal scaling on a cluster.
Java + React or Next.js frontend
The Java backend exposes a documented API consumed by web and mobile interfaces; client-side types are generated from OpenAPI.
Examples of problems solved
Memory leak or OutOfMemoryError in production
Heap dump analysis, identifying unbounded caches or listeners never released, tuning the garbage collector and container limits.
Thread pool saturated under load
Switching to Java 21 virtual threads for blocking calls, or reviewing timeouts and HTTP and JDBC connection pools.
Application stuck on an old Java version
Step-by-step migration plan: dependencies, removed APIs, javax to jakarta, regression tests, then progressive environment cutover.
Startup time too long in a container
Trimming the classpath, lazy bean initialisation, ahead-of-time compilation or a GraalVM native image depending on the case.
Frequently asked questions
Why choose Java over Node.js or Python for a backend?
Java brings strong typing, a very mature virtual machine, rich diagnostic tooling and proven enterprise libraries. It is a good fit for critical, long-lived systems handled by several teams.
Which Java version do you use?
Java 21 LTS by default on new projects. We also work on Java 8, 11 or 17 applications and propose a suitable upgrade path.
Do virtual threads replace reactive programming?
In many cases, yes. They let you write classic blocking code while supporting a large number of concurrent requests. Reactive programming remains useful for streaming and backpressure.
Can you take over a Java application with no documentation?
Yes. We start with an audit of the code, dependencies and deployments, then add characterisation tests before any structural change.
Is Java suited to containers and the cloud?
Yes. Recent JVMs respect container memory and CPU limits, and tools such as Jib, Spring Boot and GraalVM produce lightweight images that start quickly.
Related services
Java Spring Boot
Robust enterprise applications, microservices and APIs with Java and Spring Boot.
See this serviceAPI and backend
REST and GraphQL APIs, Node.js, Spring Boot and Python backend services, documented and secured.
See this serviceCustom software
Business software designed around your processes when off-the-shelf solutions fall short.
See this serviceApplication redesign
Progressive modernization of ageing applications, with no business interruption or data loss.
See this serviceCI/CD Pipelines
GitHub Actions or GitLab CI pipelines: tests, builds, automated deployments and rollbacks.
See this serviceBug Fixing
Reproduction, root cause and tested fix on your web, mobile, API and CMS applications.
See this serviceRelated expertise
Tell us about your project
Describe your need in a few lines: we come back to you with a first analysis and the next steps.