The private mempool broadcasts an auction for every transaction it receives. The auction reveals certain parts of the transaction that searchers can use to post a backrun bid.
1. Listen for Pending Auctions
Auctions are streamed over the following websocket:
Copy wss://mempool.merkle.io/stream/auctions Here is an example of an what an auction looks like:
Copy {
"chain_id": 1, // 1 (ethereum), 56 (bsc)
"id": "6397ad29b5c6edb1a7eeea18",
"transaction": {
"data": "0502b1c500000000000000000000000004969cd041c0cafb6ac462bd65b536a5bdb3a67000000000000000000000000000000000000000000002f38ca25d4a70c3ab633d000000000000000000000000000000000000000000000000282a2d9685378c260000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000100000000000000003b6d0340b767c20d9773adce84d0f0a5bc64e2f114ad3076e26b9977",
"from": "0x37a89da7BfF274F9E773418ef49caA2aFe393D70",
"gas": 355000,
"hash": "0xe3f7d4b7eb34b37e47bd54cd225c79f579d2b52869d87e7b288062ef817e9445",
"to": "0x1111111254EEB25477B68fb85Ed929f73A960582",
"value": "0",
"function_selector": "0x0502b1c5",
"logs": [
{
"address": "0x0319000133d3AdA02600f0875d2cf03D442C3367",
"data": "0x",
"topics": [
"0x5f6ebb64ba012a851c6f014e6cad458ddf213d1512049b31cd06365c2b059257",
"0x000000000000000000000000c5017be80b4446988e8686168396289a9a62668e",
"0x0000000000000000000000000f0a35351b1c5512e50c1c7410c59d5bc52bfe37"
]
}
]
},
"closes_at": "2022-12-12T22:37:32.937Z",
"created_at": "2022-12-12T22:37:28.937Z"
} 2. Submit Bids
Bids can be submitted using any Flashbot client with the relay url:
Copy POST https://mempool.merkle.io/relay However, the first transaction needs to be the hash of the target transaction, since the full transaction data is not available to you.
Bid payment is different based on chains:
Ethereum: Bids must be paid by transfer to the block builder (block.coinbase).
BSC: Bids must be paid via fee recipient transfer.
To recap, a bid is a bundle with 2 transactions:
The hash of the target transaction
For example, if we wanted to bid on the auction above, the bundle would be:
Copy [
"0xe3f7d4b7eb34b37e47bd54cd225c79f579d2b52869d87e7b288062ef817e9445", // hash of the transaction
"0x.....", // my backrun
] The full request would for this example would be:
Copy // POST https://mempool.merkle.io/relay
{
"method": "eth_sendBundle",
"jsonrpc": "2.0",
"params": [
{
"txs": [
"0xe3f7d4b7eb34b37e47bd54cd225c79f579d2b52869d87e7b288062ef817e9445", // hash of the transaction
"0x.....", // my backrun
]
}
]
} The API responds with a bid id:
Copy {
"jsonrpc": "2.0",
// bid uuid
"result": "0000-0000-0000-0000"
} 