Modify state by two calls in the same block

Hi, I got a question, Think is very important. Let’s assume I have a smart contract that modifies state (local or global). I have a call to this smart contract which can modify the state. If I have two same calls in the same block that modify the same variable, what happens?

Transactions are serialized, there is always an order to them. One will happen before the other and the second one will overwrite the first if they write to the same key. If you don’t atomically group them I don’t think you can necessarily predict which will happen first.


Ok very much thanks, I understand. Yes I’m trying to implment an acution system, and so thinking what will happen if two users bid the same thing at the same time, the highest wins in every case. Thanks!