Track 1 · Mechanics · lesson 3

The life of a transaction

9 min

You press a button in a wallet. Somewhere between there and "done" are five distinct states, and almost every confusing thing about using a blockchain happens in the gaps between them.

signedin your walletbroadcastsent to a nodependingin the mempoolincludedin a blockfinalisedcannot be undonecan be dropped here ↓
Five stages. Only the last one is genuinely permanent.

Signed

Your wallet builds the transaction — recipient, amount, fee, and a nonce counting how many transactions this account has sent — then signs it with your private key.

Nothing has left your machine yet. A signed transaction is just a file.

This account nonce is unrelated to the mining nonce from track 0. Same word, different job: this one puts your transactions in order and stops the same signed transaction being replayed twice.

It is also why transactions from one account cannot overtake each other. Nonce 7 cannot be processed before nonce 6, no matter what you pay.

Broadcast, then pending

The wallet sends it to a node, which checks it is well-formed and gossips it to its peers. Within a second or two most of the network is holding a copy.

It now sits in the mempool — waiting, visible to everyone, not yet real.

Predict

Your transaction has been pending for an hour with a fee that is now far too low. What are your options?

Choose one answer

Included

A validator picks it up and puts it in a block. Your wallet goes green.

This is the moment most people call "done". It is not, quite — and the next lesson explains why.

Finalised

After a couple of epochs, roughly thirteen minutes on Ethereum, the transaction becomes finalised: undoing it would require an attacker to destroy an enormous amount of staked ETH.

That is as permanent as anything gets.

Check

A transaction was included in a block and reverted — it ran out of gas halfway. What happens?

Choose one answer

Worth remembering

  • Five stages: signed, broadcast, pending, included, finalised.
  • The account nonce orders your transactions and prevents replay — unrelated to the mining nonce.
  • A pending transaction cannot be deleted, only replaced: same nonce, higher fee.
  • Included is not finalised. Finality on Ethereum takes about thirteen minutes.
  • A reverted transaction still costs gas and still sits on the chain forever.