Mempool

Citrea has a private mempool (memory pool) as a temporary staging area for pending transactions before they are included in a block.

Once a transaction is submitted, some basic checks are as follows:

• Is there enough space in the mempool? (see configs section below)

• Does it fit into account limits? (see configs section below)

• Does the transaction have a valid nonce that is bigger or equal than the current nonce?

• Does the address have enough balance?

If the transaction passes these checks, it is added to the mempool.

Configuration

Citrea uses a private mempool, inaccessible via RPC, which prioritizes transactions based on their fee.

Citrea mempool has custom SubPools that uses reth-transaction-pool architecture. Namely:

• Queued: Includes transactions not ready to be included in the next block due to lack of funds, nonce, etc.

• BaseFee: Includes transactions not ready to be included in the next block due to insufficient base fee.

• Pending: Includes transactions ready to be included in the next block.

For Queued, BaseFee, and Pending pools, Citrea has the 10x configuration limits compared to default values of Ethereum: 100,000 transactions per subpool with 200 MB limit.

Citrea does not have a Blob pool as it does not support blob transactions at the moment.

One more custom mempool configuration is the number of transaction slots per account, max_account_slots. Citrea has a maximum of 64 slots per account in the mempool to prevent spamming.