Remote Lead Java Developer/Solution Architect (15-week contract) in Southend-on-Sea

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.

Duration: 15 weeks

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

Working model: Mostly remote with periodic onsite attendance

Security clearance: BPSS (Baseline Personnel Security Standard) required

Residency: UK resident required

Technical Scope:

• 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.
• Architecture understanding of key management concepts.
• Infrastructure as Code — experience with Terraform or equivalent for deploying and managing application infrastructure.
• API design — ability to design clean, well-documented RESTful APIs suitable for integration by multiple consuming systems.
• Testing — experience with load/stress testing tools and approaches for validating API performance under realistic conditions.
• Technical leadership — proven ability to make architectural decisions, produce design documentation, and communicate technical trade-offs to both engineering and non-technical stakeholders.

Desirable:

• Experience designing and implementing Attribute-Based Access Control (ABAC) systems; familiarity with policy-as-code frameworks (e.g. Casbin, OPA, or XACML-based systems).
• Experience with metadata standards such as DCAT, Dublin Core, or IES.
• Experience working in UK public sector or defence environments.
• Familiarity with multi-classification or multi-tenancy access models.
• Experience with event-driven architectures and asynchronous processing patterns.
• Understanding of consistency patterns in multi-service architectures (e.g. saga pattern, eventual consistency).
• Knowledge of data mesh or federated data architecture concepts.
• Experience integrating with third-party data storage APIs (e.g. S3-compatible interfaces).

Working Context:

• The contractor will work as part of a small, focused delivery team operating within a multi-vendor programme.
• The catalogue integrates with separate data shredding/storage and encryption services delivered by other organisations — the contractor will need to collaborate across these boundaries but will not be responsible for those components.
• All work will be conducted via VPN access to the client’s cloud environment.
• The client operates within a security-conscious environment; the contractor must be comfortable working within defined information handling and access constraints.
• The role includes a knowledge transfer component in the final weeks of the engagement, including API documentation and integration guides for the client team.