How a ClientAPI Speed Test Works
In RavenDB ClientAPI, if the Read balance behavior is configured for the Fastest node , under certain conditions the ClientAPI would execute a speed test for each node, so the fastest test would be selected.
When Does it Trigger?
Once a client configuration is updated on a server, the next response from the server would include the following header:
When a client sees such a header for the first time, it will probe all nodes when the next read request will happen and store the fastest found.
After the first probe for speed, the client will repeat the speed test at most once per minute on a read request.