The 45ms latency is our internal order execution speed. Meaning, it is the latency of an order from - the moment a place order call hits our server to the moment we get an acknowledgement from the exchange.
From the user end latency, it depends upon the speed/bandwidth of the internet connection mainly.
Programming languages do not really affect this latency. But what they do, is the latency(time taken) from reading data, generating signal, applying order logics and firing the place/modify/cancel order APIs.
Choosing the programming language depends on the logic of the strategy, if you need multi-threading or not, size of parameters scanned, etc, and mainly what you’re really comfortable with