Is there a way to manually set your transaction's position in a block?

Question

I've seen some action on a coin I was monitoring on BSC using poocoin (similar to dextools but for bsc - it shows buys and sells). Whenever there was a big buy/big sell on this coin, there would be an (arbitrage? frontrun?) bot that positions their transaction exactly one position after this large trade (for example, a normal person sold a large amount at index 43 of the block, this bot would have it's index at 44 of the same block, always one position after the large sell, and makes a profit from this).

What I would like to know is how does this bot (using minimal gas) manage to always position their transaction exactly one index after a big sell? I know it's not a case of higher gas, because the bot uses normal gas fees. I've also seen bots like this on ethereum, where their transaction is always directly before/after a large trade on uniswap (for example).

Thank you.

Answer 1

in order to be on top of the big transaction, the front-runner would use more gas allocation than that big transaction. if you add even 1 wei over a trx you would be able to jump on top of it in the block index count. so that's how it is done.

Just for info, there are multiple ways being implemented to circumvent front running transactions like personalized miner networks like flashbot's network which tries to directly talk to inner nodes in order to preferably mine transactions without relying on the automatic positioning system of eth.

There is also the "The Gas Station Network" which tried to abstract the notion of gas being paid via normal eth means so technically you can pay the miner node fiat or other tokens instead of regular gas which can result in front running bots confusion.