Stream snapshots is one of the commonly used techniques to improve performance when reading long streams. Currently, developers are required to build snapshotting on their own, although it's quite clear how to do it.
ESDB can support server-side snapshots if it knows how to create a snapshot from events. Alternatively (easier) the server just deals with snapshot events and streams, for writes and reads, but the logic itself is provided by the developer via the client.
Could be one after another, if ESDB will be able to run user's code on the server node.