Lead Java Developer/Solution Architect (15-week contract)

gravity9 is seeking a Technical Lead / Solution Architect to lead the design and build of a secure metadata catalogue platform for a UK public sector client. The platform will serve as a centralised index for discovering, governing, and controlling access to data distributed across multiple independent domains — enabling authorised parties to locate and retrieve data without the catalogue itself holding or having visibility of the underlying data.

This is a greenfield build requiring strong architectural judgment, hands-on delivery capability, and the ability to work within a multi-vendor environment where the catalogue integrates with separate data storage and encryption services provided by other technology partners.

15 weeks

Half-time for the first 4 weeks (design phase); full-time for the remaining 11 weeks (build and integration)

Mostly remote with periodic onsite attendance

BPSS (Baseline Personnel Security Standard) required

UK resident required

The contractor will be responsible for leading the design and delivery of the API layer and application logic. A dedicated database consulting engineer will handle MongoDB cluster configuration, schema design, indexing, and performance tuning — the contractor will collaborate closely with them but will own the application-layer delivery.

•       Design the Attribute-Based Access Control (ABAC) model, including policy attributes (clearance level, nationality, group/role, context), enforcement points, and decision logic

•       Design the RESTful API architecture, including endpoint structure, request/response contracts, and error handling patterns

•       Map out query patterns, access flows, and integration touchpoints with external systems (data storage and encryption services provided by partner organisations)

•       Collaborate with the database consulting engineer on schema design, search strategy, and encryption approach to ensure the API layer aligns with the underlying data model

•       Contribute to Infrastructure as Code design for deployment (Terraform or similar)

•       Build a RESTful API layer in Java implementing full catalogue functionality:

–      CRUD operations for metadata records

–      Advanced search capability leveraging Atlas Search

–      ABAC enforcement on all API operations, ensuring search results and data retrieval are filtered by the requestor’s access attributes

–      Secure storage and retrieval of encrypted key material (shard keys) via CS-FLE

•       Implement unit tests to validate functional correctness

•       Build automated data load and stress testing harnesses for the combined API and cluster deployment

•       Perform integration testing against external partner systems (or appropriate stand-ins) to validate end-to-end data creation and retrieval flows

•       Produce API documentation and integration guides for consuming systems

•       Support knowledge transfer and handover activities in the final weeks of the engagement