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Fast Submit is an enhanced transaction submission mode that routes your transactions directly to BlockRazor’s Block Builder infrastructure, bypassing the standard relay path used in conventional submission flows. By eliminating intermediate hops, Fast Submit significantly reduces the time between when your transaction leaves your system and when the Block Builder receives it—resulting in measurably lower block inclusion latency and more reliable submission under high-network-congestion scenarios. For time-sensitive strategies where a few milliseconds determine whether you win or lose a block opportunity, Fast Submit is the right tool.
Fast Submit is included in the BSC Package at $1,250/month, bundled alongside Public Mempool, Block Stream, Node Stream, Call Bundle, and Tx Trace. See the Pricing page for the full package breakdown.

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How Fast Submit Works

Standard transaction submission follows a relay path: your client sends to an RPC node, which propagates the transaction through the peer-to-peer network until it eventually reaches block builders and validators. Each hop in this chain adds latency and introduces points of failure under congestion. Fast Submit replaces this with a direct channel to BlockRazor’s Block Builder nodes:
  1. Your transaction is delivered immediately to the Block Builder’s intake layer without traversing the public P2P network.
  2. BlockRazor’s multi-region infrastructure ensures the transaction reaches all Block Builder nodes with minimal inter-region propagation time.
  3. The Block Builder places the transaction into its construction pipeline for the next eligible block.
This architecture yields two primary advantages over standard submission:
  • Lower inclusion latency: Reduced round-trip time means your transaction enters the block construction pipeline faster, increasing the probability of inclusion in the very next block.
  • Higher stability under congestion: During periods of high network load, the public P2P network degrades gracefully but often unpredictably. The dedicated Fast Submit path is not affected by public mempool congestion.

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Benefits at a Glance

Reduced Inclusion Latency

Direct delivery to the Block Builder skips multiple P2P relay hops, cutting the time from submission to block construction pipeline entry.

Higher Stability Under Congestion

Bypass the public mempool entirely. Fast Submit maintains consistent delivery performance even when BSC network traffic spikes.

Works with Bundles

Use Fast Submit in combination with eth_sendBundle to get both atomic multi-transaction execution and low-latency delivery.

Included in BSC Package

No separate fee—Fast Submit is part of the $1,250/month BSC Package alongside other core Block Builder services.

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Integration Steps

1

Subscribe to the BSC Package

Log in to your BlockRazor account at https://blockrazor.io and activate the BSC Package subscription. Once active, your API key will be granted Fast Submit access on the Block Builder endpoint.
2

Build and sign your transaction or bundle

Construct your transaction locally using your preferred library (ethers.js, viem, web3.js, etc.) and sign it with your private key to produce a raw hex-encoded transaction string. If you are submitting a bundle, sign all transactions and assemble the txs array.
3

Submit to the Fast Submit endpoint

Send your JSON-RPC payload to the BlockRazor Fast Submit endpoint. Include your API key in the Authorization header. The request format is identical to eth_sendBundle or eth_sendRawTransaction depending on your submission type.
4

Monitor inclusion

After receiving the transaction hash or bundle hash in the response, poll eth_getTransactionReceipt (or use eth_traceBundle for bundles) to confirm on-chain inclusion.

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Code Example

The following example submits a raw transaction via Fast Submit using a direct POST to the BlockRazor Block Builder endpoint with the Fast Submit routing header enabled. 
const endpoint = "https://blockrazor.io/api/block-builder/fast";

// Build and sign your transaction with ethers.js or viem
const signedTxHex = "0xSIGNED_TX_HEX";

const payload = {
  jsonrpc: "2.0",
  method: "eth_sendRawTransaction",
  params: [signedTxHex],
  id: 1,
};

const response = await fetch(endpoint, {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    Authorization: "Bearer YOUR_API_KEY",
  },
  body: JSON.stringify(payload),
});

const data = await response.json();
console.log("Transaction hash:", data.result);
For strategies with extreme latency requirements, combine Fast Submit with a Dedicate Connection to reserve dedicated bandwidth and eliminate shared-infrastructure contention entirely.
Fast Submit is optimized for block inclusion latency. If your priority is protecting a transaction from the public mempool rather than minimizing latency, use eth_sendPrivateTransaction instead—or combine both approaches by using private bundle submission through the Fast Submit endpoint.

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