The API indexes Snapshot X data. Specifically, it monitors events emitted by spaces and space factories so that votes, proposals, and the deployment of new spaces can be tracked. Anyone can run the API. It uses Checkpoint and support multiple chains.
https://github.com/snapshot-labs/sx-monorepo/tree/master/apps/api
Mainnets: https://api.snapshot.box
Testnets: https://testnet-api.snapshot.box