There are mainly 2 types of order management systems: Sequential OMS and Parallel OMS.
99% of Indian brokerages use Sequential OMS, but TD Bank or Morgan Stanley uses a Parallel OMS system (you can read about all that in their 10K, I am not going into details) and Dhan did it here, I don’t know if there’s another Indian brokerage who does Parallel processing.
Since Dhan doesn’t have any legacy issues, they are going for the best set of tech.