"When buy and sell orders come into an exchange, they are first flashed to those paying to see them for 30 milliseconds — 0.03 seconds — before they are available to everyone else."

One thing I don't understand about "flash trading", and what I've never seen an explanation of in the media: How does this interact with price-time priority?

In a regular old auto-matching system, if the spread is two ticks wide and a buyer sends an order to lift best offer (instead of just improving best bid):

1. If you had a sell order at best offer in the front of the queue the time the buy came in, you're matched, and it doesn't matter if you try to cancel your sell a nanosecond later.

2. If you had no sell order, it doesn't matter if you improve the sell price a nanosecond later --- you're not matched.

So does "flash trading" change either of these? Or is it just a fancy name for "getting market data real fast" --- similar to what you'd get by colocation, but artificially enforced (e.g. they delay everyone else's data by 30ms so the "flashers" can see it first)?

(edit - formatting and grammar)