Principal Software Engineer

Java Lead Principal engineer - Java, AWS, MongoDB, Architecture, design - UK remote, Outside contract

We are working with a business who are rebuilding their core platform from the ground up and are looking for a Lead Principal Java engineer/architect who's up for a real challenge.

Their system was originally built externally, and they've now brought it fully in-house. So, your mission is to get under the hood, untangle what's there, and help them design something better - cleaner, faster, and built to scale. Someone with a forensic mind who is then able to get on with the fix. You will understand the architecture and be able to unpin what they have to design and build a better solution.

You'll work with the Tech Manager, Product Owner, and C-suite to modernise the platform and shape the next generation of features.

What You'll Be Doing

• Own the project entirely, end to end - from discovery and design to delivery and optimisation.
• Work across the stack using Java, React, AWS, MongoDB, and Elasticsearch.
• Refactor and re-engineer core components to make the platform faster, more reliable, and easier to extend.
• Collaborate closely with product and architecture teams.
• Review code, mentor teammates, and bring fresh thinking to the table.
• Write clean, well-documented code that's built to last.

• Strong experience within the Java AWS stack
• Experience modernising or replatforming legacy systems.
• Familiarity with microservices, CI/CD, or serverless architectures.
• A great understanding of modern software architecture, design principles and data structures.
• Practical experience with Java, React, MongoDB and AWS
• Curiosity and persistence - you enjoy cracking tough problems and simplifying complexity.
• The ability to balance autonomy with collaboration