user4137: Lets imagine I have UTXO sitting with some Datum, for example storing information about some USDT balance, which I am currently selling to anyone (as in lecture 8 of iteration 2).
Can there be for example 100 buyers in the same slot/block who initiated transaction with UTXO's of their balances and my one and only UTXO holding USDT for sale as input? Would these 'actions' sit in a queue of sorts and be executed one after another, while deducing currency being sold on each iteration?
If not, can anyone think of a theoretical way of allowing multiple users to buy my USDT coin on the same block/slot?
If for example I would 'shard' my selling UTXO into 100 UTXO's holding only part of total balance, how could I match buyer UTXO's with multiple partial selling UTXO's in decentralized way? I don't know, some kind of router or something.
Thank you for the answers

user1130: 
Can same UTXO be consumed multiple times in a same slot/block?

No. Nor can it ever be consumed multiple times. That's what UTxO (Unspent Transaction Output) means, it hasn't been spent yet and can only be spent once.

If not, can anyone think of a theoretical way of allowing multiple users to buy my USDT coin on the same block/slot?

This is an ongoing conversation in the community.
It really depends on what behavior you want. "Shard"ing the UTxO (as you suggest) could be a valid approach, you just need some way to minimize the chance of collision. You could include some entropy in the off-chain code to choose UTxOs at random and that could help, but collisions are bound to happen occasionally--not the end of the world, but messy.
Something I mentioned here is having off-chain services that batch requests to buy USDT. This would enable all the purchases to occur in a single transaction like what Noah Jones mentions in their answer. This kinda adds centralization, but still requires the batcher to meet the smart contracts requirements, so it's a minimal risk. There isn't a risk of extractable value either in the USDT case AFAICT, but that is something to keep in mind as well.

4137: <p>Lets imagine I have UTXO sitting with some Datum, for example storing information about some USDT balance, which I am currently selling to anyone (as in lecture 8 of iteration 2).
Can there be for example 100 buyers in the same slot/block who initiated transaction with UTXO's of their balances and my one and only UTXO holding USDT for sale as input? Would these 'actions' sit in a queue of sorts and be executed one after another, while deducing currency being sold on each iteration?</p>
<p>If not, can anyone think of a theoretical way of allowing multiple users to buy my USDT coin on the same block/slot?</p>
<p>If for example I would 'shard' my selling UTXO into 100 UTXO's holding only part of total balance, how could I match buyer UTXO's with multiple partial selling UTXO's in decentralized way? I don't know, some kind of router or something.</p>
<p>Thank you for the answers</p>
 1130: <blockquote>
<p>Can same UTXO be consumed multiple times in a same slot/block?</p>
</blockquote>
<p>No. Nor can it <em>ever</em> be consumed multiple times. That's what UTxO (Unspent Transaction Output) means, it hasn't been spent yet and can only be <em>spent</em> once.</p>
<blockquote>
<p>If not, can anyone think of a theoretical way of allowing multiple users to buy my USDT coin on the same block/slot?</p>
</blockquote>
<p>This is an ongoing conversation in the community.</p>
<p>It really depends on what behavior you want. &quot;Shard&quot;ing the UTxO (as you suggest) could be a valid approach, you just need some way to minimize the chance of collision. You could include some entropy in the off-chain code to choose UTxOs at random and that could help, but collisions are bound to happen occasionally--not the end of the world, but messy.</p>
<p>Something I mentioned <a href="https://cardano.stackexchange.com/a/3633/1130">here</a> is having off-chain services that batch requests to buy USDT. This would enable all the purchases to occur in a single transaction like what Noah Jones mentions in their answer. This kinda adds centralization, but still requires the batcher to meet the smart contracts requirements, so it's a minimal risk. There isn't a risk of <a href="https://coinmarketcap.com/alexandria/glossary/miner-extractable-value-mev" rel="nofollow noreferrer">extractable value</a> either in the USDT case AFAICT, but that is something to keep in mind as well.</p>
