I encountered a situation that made me doubt everything I know about Ethereum transactions.

In block 14721317 the transactions in positions [0, 1, 2, 3, 5, 9] all contain the same BuyOrder to buy the same NFT on OpenSea. Of course only one of them could go through, and the winner was the one in position #0.

Here comes the point: the TX in position #0 is the one with the lowest transaction fees among them! And not by little, but over 200 times smaller! I'll summarize here the gas paid by each TX here:

--- Start of block ----
Position #0: Base: 40.5 Gwei ,  Max: 333 Gwei ,  Max Priority: 5 Gwei , Gas limit: 277,845 | 203,986 (73.42%) , nonce: 3758, SUCCESS
Position #1: Base: 40.5 Gwei ,  Max: 1115 Gwei , Max Priority: 1115 Gwei , Gas limit: 350,000 | 72,556 (20.73%) , nonce: 249, REVERT
Position #2: Base: 40.5 Gwei ,  Max: 1500 Gwei , Max Priority: 500 Gwei , Gas limit: 505,000 | 72,496 (14.36%) , nonce: 387, REVERT
Position #3: Base: 40.5 Gwei ,  Max: 777 Gwei ,  Max Priority: 444 Gwei , Gas limit: 505,000 | 72,496 (14.36%) , nonce: 1763, REVERT
Position #4: Not a TX of interest
Position #5: Base: 40.5 Gwei ,  Max: 407.8 Gwei, Max Priority: 279.6 Gwei , Gas limit: 234,650 | 72,104 (30.73%) , nonce: 0, REVERT
[... not TXs of interest...]
Position #9: Base: 40.5 Gwei ,  Max: 1200 Gwei , Max Priority: 250 Gwei , Gas limit: 255,615 | 72,556 (28.38%) , nonce: 2324, REVERT
--- End of block -----

By my humble knowledge, I was quite sure that the miner would have reordered these TX he just pulled from the mempool, in a way to maximize his tx fees, but here he clearly didn't.

I know that the way TXs are put in blocks is not a standard and each miner can decide how to do it by himself, but this behavior doesn't make economic sense.

Could it be a feature to avoid front-runners? i.e. TXs order is solely based on the received time-stamp? Tho I see it very unlikely that a miner operates for the world's good and not for his economical interest.

I already looked at this older post , where the only point that I see could apply is the following, but I think its highly unlikely - tho I'm running a blockchain analysis to rule that out.

Transactions that origin from the miner node will be put first.

What am I missing?

1 Answer 1


It's a private transaction. Basically a transaction that was fed directly to the miner, not through the mempool.

Miners earn more through MEV, either running their own code to take value from mempool (frontrun, backrun, etc) or rent their mining service to external source of transactions, called private transactions.

There are also services like bloXroute who have a private BDN (block distribution network), allowing them to propagate blocks faster and offer private transactions to their customers.

Welcome to the Dark Forest.

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