You can access your Macrometa data collections by writing a query in SQL or C8QL. GDN stores named and parameterized queries as query workers that you can run from a dedicated REST endpoint.
When the user saves a query, the query is automatically converted to an API and is deployed globally to serve the users from the region closest to them with local latencies.
Best practice is to use query workers to build applications integrated with GDN instead of directly querying C8QL. For more information, refer to Query Workers.