Lead Java Developer/Solution Architect (6-month contract)

gravity9 is recruiting Java engineers and architects for a portfolio of engagements across UK central government. These are large-scale, data-intensive modernisation programmes: replacing legacy systems that carry statutory weight, decomposing monoliths that serve millions of users, and building secure data platforms where access control and auditability are first-class architectural concerns rather than late additions. We are hiring across two overlapping profiles — Senior Java Developer and Application / Migration Architect — and expect most people to move between programmes as engagements start and complete. Several of these are hands-on architect roles: you will own design decisions and also write production code The kind of work The following are representative of current and upcoming engagements. Individual roles will draw on some of this, not all of it — we are more interested in engineers who can work confidently at the intersection of Java and data than in a checklist match against any one programme. Secure data catalogue and access-control platform A greenfield metadata catalogue acting as a federated index over data held across independent domains, so that authorised parties can locate and retrieve data the catalogue itself never holds. The work includes designing an attribute-based access control model over attributes such as clearance, nationality, organisational unit and compartment; enforcing those policies inside the database query path rather than filtering results afterwards; application-layer encryption with externally managed keys; hybrid lexical and semantic search with access filtering applied before candidate retrieval rather than after it; and a tamper-evident audit trail that can reconstruct why a given record was returned, redacted or withheld. Real-time decision-support data architecture Replacing point-to-point integration across a multi-vendor estate with a microservices architecture and a common data layer, so that operational data flow