To sort transactions fairly:
There is an “open secret” in blockchain design today, which is that the blockchain is actually centralized for a short period of time. Miners and validators can order transactions as they wish. Users in the network can also influence the ordering of transactions by paying transaction fees (eg gas fees in Ethereum), and to a certain extent take advantage of the speed of the network connection. This type of manipulation can take the form of front-running transactions. Miners watch user transactions and prepend their own transactions in the same block for personal gain. They do this by taking advantage of the fact that they can see the transaction pool ahead of time to extract the benefits of their users. For example, a bot could be developed that inserts a buy transaction before a user's transaction. In this way, users can make a profit by buying before the user's buy order drives up the price of the asset.