Senior Java Software Engineer

Connect AI; Warminster; Hybrid; GBP 80,000 - 120,000; Full time

Job summary

Connect AI in the Warminster area is seeking a Senior Backend Engineer to own backend services in a Java/Spring Boot stack, operating in AWS and microservice architecture.

You will design, implement and evolve production-grade services, with ownership from design to deployment, working in a hybrid model 3 days onsite. Security clearance can be required for this defence programme, reflecting the mission-critical context.

Qualifications

• Strong commercial experience building backend systems with Java and Spring Boot.
• Experience with microservices or distributed systems.
• REST API design experience.
• PostgreSQL or similar relational databases.
• AWS or another major cloud platform.
• CI/CD and automated testing practices.
• Docker and Kubernetes experience.
• Event-driven architectures using Kafka or similar messaging.

Responsibilities

• Design, build and evolve backend services within a modern distributed architecture.
• Contribute to system design and take ownership from design through production.
• Review code and participate in technical design discussions to improve standards.

Skills

Java

Spring Boot

REST APIs

PostgreSQL

Kafka

AWS

Docker

Kubernetes

CI/CD

JUnit / Mockito / TDD

Tools

Kafka

Docker

Kubernetes

Job description

Senior Backend Engineer — Java / Spring Boot / AWS

£80,000–£120,000 | Permanent | Hybrid – Warminster area, 3 days onsite

I’m partnering with a global software product business delivering mission-critical platforms across defence, government and resilience.

They’re expanding the engineering team behind a major, multi-year UK defence programme and are looking for a Senior Backend Engineer who wants more than another maintenance-heavy Java role.

This is an opportunity to work on complex, production-grade systems where reliability, scalability and engineering quality genuinely matter, with real ownership over architecture, technical decisions and how the platform evolves.

What you’ll be working on

You’ll design, build and evolve backend services within a modern distributed architecture, working closely with experienced engineers, technical leads and product stakeholders.

The environment includes:

• Java 17+ / Java 21
• Spring Boot
• REST APIs
• PostgreSQL
• Kafka / event-driven architectures
• AWS
• Docker & Kubernetes
• CI/CD
• JUnit / Mockito / TDD
• Microservices and distributed systems

You won’t simply be handed tickets.

You’ll be expected to contribute to system design, challenge technical decisions, improve engineering standards and take ownership of software from design through to production.

What they’re looking for

You’ll likely have strong commercial experience building backend systems with Java and Spring Boot, alongside good knowledge of APIs, databases and distributed architectures.

They’re particularly interested in engineers who can demonstrate experience with:

• Building production Java / Spring Boot services
• Microservices or distributed systems
• REST API design
• PostgreSQL or similar relational databases
• AWS or another major cloud platform
• Docker / Kubernetes
• Messaging technologies such as Kafka or RabbitMQ
• Automated testing and clean engineering practices
• Code reviews and technical design discussions

Experience within defence, aerospace, government, fintech, healthcare or another highly regulated / mission-critical environment would be useful, but isn’t essential.

Why it’s interesting

The attraction here is the level of technical ownership.

You’ll be joining a programme with long-term investment behind it, working on software that has genuine operational importance rather than another short-lived internal application.

There is also scope to influence:

• Architecture and system design
• Engineering standards
• Technical debt reduction
• Reliability and scalability
• Development practices
• Future technical direction

For engineers looking to progress towards Staff / Technical Lead level, there is plenty of room to increase your influence while remaining hands-on.

Package

Salary: up to approximately £120,000, depending on experience

Contract: Permanent

Location: Warminster area

Hybrid: approximately 3 days per week onsite

Due to the nature of the programme, candidates will need to hold or be eligible to obtain UK security clearance.