The main concern when using a DEX is the speed. Users that have interacted with a DEX before, will remark the uncomfortable experience of waiting for their trade to confirm on the blockchain or having the trade fail because someone else has traded the order and losing the gas fees.
DMEX solves this problem by employing a Hybrid DEX model, where the order book and matching engine is stored on a centralized server while the funds and transactions are recorded on the blockchain. This allows for instant order execution (no need to wait blockchain confirmations) and prevents front-running as all trades are pushed in FIFO (first-in-first-out) order to the blockchain by the matching engine.
The matching engine also tracks the order fills and will not match orders that are already filled and awaiting to be recorded. The user receives instant trade confirmation.
On traditional centralized margin trading exchanges the positions are liquidated using the internal exchange price which opens up the possibility for the exchange owners to manipulate the price in order to liquidate your position early.