Curriculum·J302 Swap Execution: AMMs, MEV, and DEX Architectures·about 32 min
The transaction lifecycle
By the end of this lesson you can
- →Trace a transaction from signing to finality and name what can change at each stage
- →Explain why confirmed is a probability rather than a state
- →Compute the window during which your intent is public and actionable by others
- →Manage nonce ordering so that one stuck transaction cannot block an exit
Junior · enrolled learners
This lesson opens with The seven block reorganisation, 25 May 2022.
- What happened
- At 08:55 UTC on 25 May 2022, seven blocks on the Ethereum beacon chain, numbered 3,887,075 through 3,887,081, were removed from the canonical chain between 08:55:23 and 08:56:35. The cause was not a flaw in the fork choice rule. A proposer boost update, which gives the current slot's proposer a weight advantage so that attesters prefer timely proposals, had been released as a change operators could adopt at their own pace. Some validators were running it and some were not. A late arriving block then split the two groups' views, and the resulting disagreement resolved by discarding seven blocks that had already been produced and seen.
- The decision point
- Everything in those seven blocks had appeared, to anybody watching, to have happened. Wallets showed confirmations. Explorers showed transactions. Seventy-two seconds later the state containing them was not the state the network agreed on. Nothing was hacked and no rule was violated, and the trigger was that a routine, optional client upgrade had reached some operators and not others, which is a property of every network running more than one version of anything.
What you will be able to answer
- →What does one confirmation mean?
- →When is an Ethereum transaction actually final?
- →What is the mempool exposure window?
- →Why does a stuck transaction block everything?
Orientation and Year One are open: anyone can read them without an account. From Year Two onward the lessons are for enrolled learners, because progress through the later years only means anything if it is tracked against a record.
It is free. We do not sell the list and there is nothing to buy at the end of it.
Sources and review
- https://barnabe.substack.com/p/pos-ethereum-reorg
- https://cointelegraph.com/news/ethereum-beacon-chain-experiences-7-block-reorg-what-s-going-on/amp
- https://collective.flashbots.net/t/post-mortem-april-3rd-2023-mev-boost-relay-incident-and-related-timing-issue/1540
- https://ethereum.org/en/developers/docs/transactions/
Confidence high·Volatility medium·Reviewed 2026-08-06·Owner unassigned
Contested
Slot times, finality rules and mempool behavior differ by chain, and the specific figures here describe Ethereum. The structure of the lifecycle, being signed then public then included then agreed, is general, and the confirmation policies of venues encode each chain's own answer.
Whether private transaction routing is a net improvement is genuinely contested and is treated in J302-04. It removes public mempool exposure and substitutes trust in the party receiving the transaction, which is a trade rather than a fix.