🔵Base L2 Index (Coming soon)

This index tracks thegas_spent_per_block for Base L2 blocks. It sums up the total gas spent per transaction across a block, as defined as:

$$\text{Total Gas Spent Per Transaction} = \text{(Effective GasPrice} \times \text{GasUsed)} + \text{L1 Fee}$$

Breaking down a Base transaction

Using this transaction as an example

What exactly is included in the index calculation?

Value	Definition
Gas price	This is the Gas price that the user paid for the Base L2 transaction. This includes both Priority Fee and Base Fee (Note: this is a term inherited from ETH, not the Base L2)
Gas usage by txn	The actual gas unit that the transaction consumes
L1 fee	The total amount of fee the transaction pays to post on Ethereum L1. This is not equal to L1 gas price x L1 gas used

Edge case: Transactions without L1 fee

There are two type of 0 l1_fee tx, System and Legacy. There are no more Legacy-type tx after March 2024. All 0 l1 fee transactions are System type. We can treat the l1Fee as 0.

Legacy type is 126 in the type field

Edge case: Block re-org

Currently, all L2 data that comes from L1, such as deposits, are processed only after being confirmed in an L1 block. Therefore, there haven't been any reorganizations caused by L1 reorgs or hard forks yet. Since there is currently a single sequencer, uncle blocks or forked blocks do not exist either.

Source

• https://github.com/ethereum-optimism/developers/discussions/510#discussioncomment-9981674

• https://github.com/ethereum-optimism/developers/discussions/450#discussioncomment-9720241

• https://specs.optimism.io/protocol/derivation.html?highlight=reorg#resetting-the-pipeline

Failsafe for re-org

To be absolutely safe, we can also query the latest finalized block, for example:

curl https://docs-demo.base-mainnet.quiknode.pro/ \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"method":"eth_getBlockByNumber","params":["finalized",true],"id":1,"jsonrpc":"2.0"}'

What is excluded from the index calculation?

Value	Definition
Gas fees (Base)	The fee transaction has to pay at the time of the block
Gas fees (Max)	The maximum of total gas the user is willing to pay for the transaction
Gas fees (Max priority)	The maximum of gas the user is willing to pay to the validator for the transaction
Gas limit	The maximum amount of computational work a user is willing to pay for in a single transaction
L1 gas used by txn	The amount of gas units that the transaction consumes when posted on ETH L1
L1 gas price	The gas price on Ethereum L1 that this transaction pays
L1 fee scalar	This is a preventative premium in case L1 gas fee spikes
Transaction fee	The total amount of gas fee the user pays for the transaction. Transaction fee = L2 base fee + L2 priority fee + L1 fee = (Gas usage x Gas price) + L1 fee

Querying the data

Query from Base nodes from Quicknode.

Query	RPC Method	Description
Block	eth_getBlockByNumber	Fetch full transaction object from a block by block number Iterate all transactions and get the hash of each transaction
TransactionReceipt	eth_getTransactionReceipt	Fetch transaction Receipt using the hash from above

Sample response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "blockHash": "0x7ab08ca50352724d43982b714b8df7d49198f0c19249687275be78b609431668",
    "blockNumber": "0x156cf89",
    "contractAddress": null,
    "cumulativeGasUsed": "0x17e3433",
    "effectiveGasPrice": "0x1af57f6",
    "from": "0x79c88d58666313fc39b1929294376af298dd8c14",
    "gasUsed": "0x78e9",
    "l1BaseFeeScalar": "0x8dd",
    "l1BlobBaseFee": "0x1ce2291bd",
    "l1BlobBaseFeeScalar": "0x101c12",
    "l1Fee": "0xca71da6f35",
    "l1GasPrice": "0x3441aa4ca",
    "l1GasUsed": "0x640",
    "logs": [
      {
        "address": "0xc5bf05cd32a14bffb705fb37a9d218895187376c",
        "topics": [
          "0x5548c837ab068cf56a2c2479df0882a4922fd203edb7517321831d95078c5f62",
          "0x00000000000000000000000079c88d58666313fc39b1929294376af298dd8c14",
          "0x0000000000000000000000000000000000000000000000000000000000000000"
        ],
        "data": "0x000000000