Hydra Indexer Gateway is a hasura based GraphQL server exposing the indexed Substrate data (primarily, extrinsics and events), indexed by Hydra Indexer.
Hydra Indexer Gateway is distributed as a set of docker containers. Please have a look at https://github.com/subsquid/hydra-template/blob/main/indexer/docker-compose.yml for an example of how to setup your own indexer instance.