Just remembered, another issue with lag used to be this, after an order is placed Dom freezes for a while & when it starts updating again it plays back price changes at x multiple original speed. That was totally unreliable & unusable, I know X_trader is a sophisticated bit of kit, but I couldn't understand or believe the broker, because there was no ping issues with my charting from IQ Feed. Signal travels via same Internet provider and X-Trader had latency issues & IQ Feed didn't. That's why I couldn't believe what broker was telling me about latency.
Quote from Hoi:
Incorrect !
Because we are talking here about Lag! Lag defined as history. (thiink about this very hard before you reply...).
In your example you simply do not receive the quote from 150ms ago at all. If you did, then yes that would be Lag, but you don't!
You simply get a foto-picture each 166ms of that current situation, and this photo-picture doesn't have any Lag as it is the current picture. Therafter you don't get ANY quotes for the next 165ms before you get a next photo-picture of the THEN current situation.
So you don't get history nor Lag, you simply don't get all quotes like a streaming-data-provider.
In other words:
a) Snapshotting doesn't Lag, not even at times of high volatile newsbreaks (because sending pictures to hundreds of thousands clients doesn't jam resources).
b) Snapshotting is suitable for fast-trading but not for charting (for that use a streaming-data-provider, which lags but offers all quotes).
Needles to say: but of course I would like to have a faster snapshotting-frequency as well.