Codestin Search App

Introduction

Flashblocks on Base are a transaction preconfirmation feature that provides near-instant transaction feedback by streaming partial block updates every 200 milliseconds. This significantly reduces the effective block time from Base’s standard 2 seconds to just 200 milliseconds, a 10x increase.

Flashblocks is great for developers who demand instant UX such as decentralized exchanges, onchain gaming, and other high-frequency applications.

Getting started instructions

Flashblocks is currently supported on both Base testnet and mainnet and can be accessed using your existing Alchemy Base RPC.

Network	Flashblocks Availability
Base Sepolia	✅
Base Mainnet	✅

Flashblocks-enabled API Endpoints

eth_getBlockByNumber

Use the pending tag to retrieve the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["pending",true],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": {
>     "number": "0x1234",
>     "hash": "0x...",
>     "transactions": [...]
>   }
> }

eth_getTransactionReceipt

Use the existing receipt RPC to get preconfirmed receipts:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getTransactionReceipt","params":["0x..."],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": {
>     "transactionHash": "0x...",
>     "blockNumber": "0x1234",
>     "status": "0x1"
>   }
> }

eth_getBalance

Use the pending tag to get the address balance in the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getBalance","params":["0x...","pending"],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": "0x0234"
> }

eth_getTransactionCount

Use the pending tag to get the address nonce in the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getTransactionCount","params":["0x...","pending"],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": "0x1b" // 27 transactions
> }

eth_getTransactionByHash

Use the existing get transaction by hash RPC to get preconfirmed transactions:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","params":["0x..."],"id":1}'

Example Response

$ {
>   "type": "0x2",
>   "chainId": "...",
>   "nonce": "...",
>   ...
> }

eth_call

Use the pending tag to execute a smart contract call against the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_call","params":[{"to":"0x...","data":"0x..."},"pending"],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": "0x0000000000000000000000000000000000000000000000000000000000000001"
> }

eth_simulateV1

Use the pending tag to simulate transactions against the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_simulateV1","params":[{"blockStateCalls":[{"calls":[{"to":"0x...","data":"0x..."}],"stateOverrides":{}}],"traceTransfers":true,"validation":true},"pending"],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": [
>     {
>       "calls": [
>         {
>           "status": "0x1",
>           "gasUsed": "0x5208",
>           "returnData": "0x"
>         }
>       ]
>     }
>   ]
> }

eth_estimateGas

Use the pending tag to estimate gas against the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_estimateGas","params":[{"to":"0x...","data":"0x..."},"pending"],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": "0x5208"
> }

eth_getLogs

Use the pending tag for toBlock to retrieve logs from the latest Flashblock:

$ curl https://base-sepolia.g.alchemy.com/v2/<YOUR_API_KEY> -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_getLogs","params":[{"fromBlock":"latest","toBlock":"pending","address":"0x...","topics":["0x..."]}],"id":1}'

Example Response

$ {
>   "jsonrpc": "2.0",
>   "id": 1,
>   "result": [
>     {
>       "address": "0x...",
>       "topics": ["0x..."],
>       "data": "0x...",
>       "blockNumber": "0x1234",
>       "transactionHash": "0x...",
>       "transactionIndex": "0x0",
>       "blockHash": "0x...",
>       "logIndex": "0x0",
>       "removed": false
>     }
>   ]
> }

Also check out the Official Base Flashblocks Docs!