Koios is a low-level, asynchronous, GCP-compliant search engine for Generation Challenge Programme research data, analysis and visualization tools. Koios provides a high level facade for GCP datasources. The Koios Engine is primarily a query wrapper of the GCP Datasources and is used by Zeus for its structured result set management. The API can be found here: Koios API.
For pertinent technical documentation on the Zeus, and the framework it has built on, please refer to the Zeus Documentation in the GCP Pantheon website.