Bid on transactions

Searchers bid on transactions by submitting bundles that include the hash of the target transaction and a backrun transaction that pays the bid amount to the fee recipient.

Step 1: Construct a backrun bundle

A bundle has 2 transactions:

• The hash of the target transaction: make the first element of the transactions array in params of eth_sendBundle the hash of the pending target, instead of the fully encoded transaction.
• Your backrun: the backrun must pay the fee_recipient the bid with an Ether transfer.

Step 2: (Optional) Simulate your bundle

Before submitting your bundle, you can use the eth_callMany method to simulate it against a specific block number. This helps verify that your bundle will execute correctly before you submit it.

The eth_callMany method allows you to simulate a bundle at the top of the next block, helping you:

• Verify your bundle will execute successfully.
• Check return values and state changes.
• Test against different block numbers.

Request fields

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_callMany",
  "params": [
    {
      txs,               // Array[String], A list of signed transactions to execute in an atomic bundle
      blockNumber,       // String, a hex encoded block number for which this bundle is valid on
      stateBlockNumber,  // String, either a hex encoded number or a block tag for which state to base this simulation on. Can use "latest"
      timestamp,         // (Optional) Number, the timestamp to use for this bundle simulation, in seconds since the unix epoch
    }
  ]
}

Example request

curl -X POST https://rpc.mevblocker.io/fast \
  -H "Content-Type: application/json" \
  -d '{
  "jsonrpc": "2.0",
  "method": "eth_callMany",
  "params": [[{
    "transactions": [{
      "from": "0xDAFEA492D9c6733ae3d56b7Ed1ADB60692c98Bc5",
      "to": "0xdAC17F958D2ee523a2206206994597C13D831ec7",
      "gas": "0x92c0",
      "gasPrice": "0x7896e72a000",
      "value": "0x0",
      "data": "0x70a0823100000000000000000000000047ac0fb4f2d84898e4d9e7b4dab3c24507a6d503"
    }],
    "blockOverride": {
      "blockNumber": "0xe39dd0"
    }
  }], {
    "blockNumber": "0x103434E",
    "transactionIndex": 234
  }],
  "id": 1
}'

Example response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": [[{
    "value": "000000000000000000000000000000000000000000000000000470de54da7138"
  }]]
}

Step 3: Submit the bundle

Send the backrun bundle to the wss://searchers.mevblocker.io websocket connection using the eth_sendBundle method.

Example request

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_sendBundle",
  "params": [
    {
      "txs": [
        "txHash", // originator transaction
        "rawTxHex" // searcher transaction
      ],
      "blockNumber": "0x102286B",       // (Optional) String, a hex-encoded block number for which this bundle is valid. Default, current block number
      "replacementUuid": "blinklabsxyz",   // (Optional) String, any arbitrary string that can be used to replace or cancel this bundle
    }
  ]
}

Example response

{
    "id": 1,
    "jsonrpc": "2.0",
    "result": "0x164d7d41f24b7f333af3b4a70b690cf93f636227165ea2b699fbb7eed09c46c7"
}