As proposed by Codex, we can reduce lag when sampling in the happy path by sending DataColumnsByRoot requests immediately as we see the block and having the sampling provider hold the request until it gets the sample.

This mechanism is already implemented in our end, both the eager sending, and the holding of requests. However, we are bound by the ReqResp timeout, which may be too short depending on how wide the sampling window is. We may artificially extend the deadline by sending the first byte of data.