Transaction lifecycle
Finality has two definitions on Linea:
- Soft finality: The transaction is confirmed on Linea. This takes two seconds, i.e Linea's block time. See step 3. For simplicity, Linea is guaranteed to not reorg—remove competing versions of blockchain history in favor of a canonical one—when there are reorgs on L1.
- Hard finality: The proof submitted to L1 has been verified, and two epochs have elapsed. The typical time before hard finality is 6-32 hours, although the six-hour minimum will be reduced to zero in future. See step 6.
Transactions on Linea proceed through the following steps:
Step 1: Submission​
This is where every transaction originates: at the wallet level, a user signs a transaction and broadcasts it to Linea. From here, transactions head straight to the mempool, similarly to Ethereum, where they become pending transactions.
Step 2: Block building​
The Linea sequencer is responsible for ordering, building, and executing blocks. For each transaction added to the mempool, the sequencer checks its validity, rejecting transactions as necessary. Transaction validity conditions are specific to Linea, and differ slightly from those on other networks, including Ethereum.
The sequencer orders transactions according to the priority fee paid for each, a method known as a priority gas auction. So, having passed the above checks, valid transactions are placed into blocks in the correct sequence and executed.
At this point, the transaction's lifecycle is more or less complete — at least from a user perspective. The block containing the transaction has been added to the "head" of the Linea blockchain—the most recent block—and a transaction receipt is returned to the user's wallet as confirmation.
However, the transaction and its associated data will continue to be processed in order to generate ZK proofs. Let's press on.