Why is there a delay in order execution during the market opening?
Two things determine the speed of order execution at market open -
1. Exchange capacity to handle orders.
If the number of orders hits the maximum orders the exchange can handle, then the exchange lines can get choked, and your order can take up to few seconds to go through.
2. Order queue from the broker.
Every broker is connected to exchanges via leased lines. These lines have a certain order per second capacity. If the order capacity is breached, they get in a queue, and the orders can take a few seconds to go through.
When the market opens, either of the two can happen and delay your order execution.