Relay

Relay is an application developed by the University of Nottingham that enables federated cohort discovery across health data networks.

The code for Relay is open source, and can be found on Github.

Core Functionality

Relay coordinates Cohort Discovery queries across a federated network of subnodes. It can fetch queries from any compatible Upstream Task API and then - after federating those queries to any compatible Downstream Task API clients - aggregates the returned results into a single response, which is sent back Upstream.

To support data governance, Relay applies configurable obfuscation techniques such as suppression or rounding, ensuring sensitive counts are protected. It is designed for resilience, returning aggregated results even if one or more nodes are unavailable.

Use in Federated Research

Relay is deployed in a centralised environment to form a connected network of subnodes, each typically running its own Cohort Discovery system. This architecture enables distributed datasets to be queried as though they were one, without sharing patient-level data.

By aggregating results centrally, Relay allows institutions to collaborate on large-scale research while maintaining data sovereignty and privacy.

Integration and Extensibility

Relay integrates seamlessly with any Task API–driven workflow, allowing coordinated queries across multiple nodes. Its open-source nature means it can be extended, adapted, and embedded into existing research infrastructures to support a range of governance and interoperability needs.

Ideal Use Cases

• Multi-site cohort discovery for clinical trials or observational studies
• Feasibility assessments without sharing raw data
• Privacy-preserving network coordination with built-in resilience to node outages

Relay is open-source, containerised, and security-conscious—enabling ethical, scalable health research through federated collaboration.