Quoting Mr. Nithin
"One of the issues that we and other brokers place is of orders placed at market opening taking a long time to execute. The main reason for this is the thousands of after market orders that get fired at the market opening, these will get in a queue and even the market orders getting placed at 9.15 am would take a long time to execute.
We did the below to fix this issue
Equity AMO orders are placed at pre-market open (@9.00 am) instead of normal market open at 9.15 am. This we have done a few weeks back. Equity orders which sometimes was taking upto 30 seconds at market open to execute now trades instantly."