Do miners have to verify blocks?

Question

I want to know whether the bottom layer of Ethereum requires miners to verify blocks?

The reason for this problem is that I have been thinking about a scenario of blockchain transaction verification recently: If the api provided by chainLink is called in the smart contract, it is necessary that the contract address has enough tokens for payment. When the block containing this transaction is broadcast, other miners will verify the transaction in the block. When the miner verify the transaction in the new coming block, he need to call the smart contract. What if the contract address does not have enough tokens? Will miners continue to verify this transaction?

Hope you can give me some help, thanks!

Answer 1

Short answer is no but they do.

See https://ethereum.stackexchange.com/a/45187/405 for a deeper explanation of the process.

But as explained, it is because they would take too many risks not to validate each transaction in a block. It's game theory. If a miner was pushing a block with invalid transactions by not validating them, it would be detected by others and the block would be rejected by the network. The miner would have mined for nothing and mining for nothing is loosing money.

So yes for fun you can try not validating before pushing a block. It seems some do it as they bet on the tx being valid most of the time. But it's dangerous and not worth it IMO as the validating part is clearly not the one that uses a lot of energy (only a few hundreds of milliseconds).

In your case, miner will likely reject the transaction as soon as running it and will raise an error because of the low balance of the address at this block number. Miner will not select the transaction for the new block and will add another one from the pool instead.