Please bear in mind that following is my best guess. Here we can see the following:
With trades typically taking ∼ 2ms from your VPS to us and our LPs processing them in less than 4ms… get there, faster!
This means that once your request reaches Darwinex servers, they process it in ~4ms. So the limiting factor aside from this is YOUR LATENCY to darwinex servers. This depends on many factors -> your internet quality, your location, time of the day (your network might be congested) etc.
How to check this latency? Mind, I don't trade with darwinex, just invest here, but THIS thread explains how to check latency in MT4 platform - so I guess you can find out that way.
If you are asking about processing time from your trade to your DARWIN INVESTORS replication (if you are darwin provider) you can click on "Investors" part of any darwin and see latency for last 100 or so trades.
Short answer: Your latency + 4ms.