The observer service provides read-only access to the Flow network. It implements a subset of the Access API which is served from a local copy of the protocol data. It can be configured to proxy the remaining endpoints to an upstream staked Access Node.

At a high level it does the following:

1. Follows updates to the Flow network's protocol state, and maintains a local copy.

2. Runs a gRPC server which implements a subset of the Access API

   1. Responds to API calls for information such as GetBlockByID, GetCollectionByID, GetTransaction etc using its local data

   2. Forwards requests for execution state (ExecuteScriptAt*, GetEvents*, TransactionResult, etc) to a configured upstream staked Access Node.

NOTE: The Observer service does not participate in the Flow protocol