Optimism Flashblocks.

Flashblocks-specific RPC methods, WebSocket subscriptions, and the infrastructure stream schema for Optimism pre-confirmations.

Optimism runs on the OP Stack (chain ID 10), the reference implementation for which Flashblocks' Rollup-Boost sidecar was built. Flashblocks are available on Optimism Mainnet and Optimism Sepolia (chain ID 11155420), served over the standard Optimism RPC interface so existing tooling reads preconfirmed state without modification.

Endpoints

Transport

URL

HTTP

https://go.getblock.io/<ACCESS-TOKEN>/

WebSocket

wss://go.getblock.io/<ACCESS-TOKEN>/

The pending tag works over HTTP. Flashblocks subscriptions require the WebSocket endpoint.

Flashblocks-Aware Methods

Method

Usage

eth_getTransactionCount

Pass "pending" for a nonce that accounts for Flashblock transactions

eth_getStorageAt

Pass "pending" for storage at preconfirmed state

eth_getBalance

Pass "pending" for the balance at the latest Flashblock state

eth_getBlockByNumber

Pass "pending" to retrieve the current Flashblock

eth_getBlockReceipt

Pass "pending" to get receipts for all pre-confirmed transactions in the current Flashblock.

eth_getBlockTransactionCountByNumber

Pass "pending" to get the count of pre-confirmed transactions in the current Flashblock.

eth_estimateGas

Pass "pending" to estimate gas against preconfirmed state

eth_call

Pass "pending" to execute against preconfirmed state

eth_simulateV1

Simulates against the latest preconfirmed state

eth_getLogs

Pass "fromBlock": "pending" and "toBlock": "pending" to query logs from pre-confirmed transactions, updated every ~200ms.

eth_getCode

Pass "pending" for contract code at preconfirmed state

eth_subscribe

Opens a Flashblocks WebSocket subscription

eth_unsubscribe

Cancels an active Flashblocks subscription

Example

The example below reads the pending balance of the Optimism WETH contract 0x4200000000000000000000000000000000000006. Substitute any supported method and parameters; the "pending" tag is what selects Flashblock state.

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "eth_getBalance",
    "params": ["0x4200000000000000000000000000000000000006", "pending"],
    "id": "getblock.io"
}'

example.js

const axios = require('axios');

const response = await axios.post('https://go.getblock.io/<ACCESS-TOKEN>/', {
    jsonrpc: '2.0',
    method: 'eth_getBalance',
    params: ['0x4200000000000000000000000000000000000006', 'pending'],
    id: 'getblock.io'
}, {
    headers: { 'Content-Type': 'application/json' }
});

console.log(response.data.result);

example.py

import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'eth_getBalance',
        'params': ['0x4200000000000000000000000000000000000006', 'pending'],
        'id': 'getblock.io'
    }
)

print(response.json())

example.rs

use reqwest::Client;
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();

    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "eth_getBalance",
            "params": ["0x4200000000000000000000000000000000000006", "pending"],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;

    println!("Result: {}", response["result"]);
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x0de0b6b3a7640000"
}

The result is the hex-encoded balance in wei at the latest Flashblock. The same request with the "latest" tag returns the value at the last sealed block.

Use Cases

Trading Platforms: Surface preconfirmed order and swap results with sub-second latency.
Prediction Markets: Reflect changes in market state as soon as transactions are preconfirmed.
Wallets: Show instant transaction feedback and real-time balance updates before a block is sealed.
Nonce Management: Use eth_getTransactionCount with pending to avoid nonce collisions during rapid submission.
Preconfirmed Receipts: Poll eth_getTransactionReceipt to confirm inclusion at Flashblock cadence.

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Last updated 4 days ago

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