Flashblocks

Flashblocks lets you receive early transaction confirmation signals without waiting for the next block to be produced. This enables real-time responsiveness for apps that require fast user feedback.

What is Flashblocks?

When you submit a transaction on GIWA, it is normally confirmed once it is included in a block. Since GIWA produces a block roughly every 1 second, this confirmation time can take up to one full block interval. (and may be longer during network congestion.)

Flashblocks improves this experience by providing preconfirmations—instant signals that arrive up to ~200ms after you send a transaction. Instead of waiting for the next block to be produced, users can receive fast feedback about whether their transaction is likely to be included.

Flashblocks does not create blocks faster. It simply gives you an earlier view of transaction status before the block is sealed.

This makes Flashblocks especially useful for:

• Wallets and web services that want immediate transaction feedback

• Payment services that want fast checkout experiences

• Games and real-time applications that require responsive UX

Using Flashblocks

Flashblocks RPC works just like the standard Ethereum JSON-RPC interface. To use it, your RPC provider must support Flashblocks mode—these are called Flashblocks-aware RPC endpoints.

Flashblocks-aware RPC

GIWA provides Flashblocks-aware RPC endpoints for development and testing:

Network	Endpoint
GIWA Testnet (Sepolia)	​https://sepolia-rpc-flashblocks.giwa.io​
GIWA Mainnet	🚧 Coming soon

The endpoint above is intended for development and testing and is rate-limited. For production applications, we recommend using an external node provider or running your own Flashblocks-aware RPC node.

Supported RPC Methods

Below are common RPC methods that support Flashblocks. Most methods use the pending block tag to return data from the latest flashblock state.

eth_call

Executes a smart contract call against the latest flashblock state using the pending tag.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_call",
    "params": [{"to": "0x...", "data": "0x..."}, "pending"],
    "id": 1
  }'

Response

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

eth_estimateGas

Estimates gas usage based on the latest flashblock state using the pending tag.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [{"to": "0x...", "data": "0x..."},"pending"],
    "id": 1
  }'

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x9425"
}

eth_getBalance

Returns an address’s balance in the latest flashblock state using the pending tag.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getBalance",
    "params": ["0x...", "pending"],
    "id": 1
  }'

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x1234"
}

eth_getBlockByNumber

Retrieves the most recent flashblock when pending is used.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getBlockByNumber",
    "params": ["pending", true],
    "id": 1
  }'

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "number": "0x1234",
    "hash": "0x..",        // Even for the same block, the hash may change if the set of preconfirmed transactions changes
    "transactions": [...], // All preconfirmed transactions included in the flashblock
    "stateRoot": "0x...",
    "gasUsed": "0x...",
    "timestamp": "0x..."
  }
}

eth_getLogs

Retrieves logs from the latest flashblock state using the pending tag.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -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
  }'

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
    }
  ]
}

eth_getTransactionCount

Returns the nonce of an address from the latest flashblock state using the pending tag.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionCount",
    "params": ["0x...", "pending"],
    "id": 1
  }'

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x12"
}

eth_getTransactionByHash

Returns transaction information based on a hash, including flashblock-specific details.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionByHash",
    "params": ["0x..."],
    "id": 1
  }'

Response

{
	"jsonrpc": "2.0",
	"result": {
		"blockHash": "0x...",
		"blockNumber": "0x1234",
		"chainId": "0x164ce",
		"nonce": "0x23",
		"transactionIndex": "0x3",
		"type": "0x2",
	},
	"id": 1
}

eth_getTransactionReceipt

Returns a transaction receipt from the flashblock state (preconfirmed).

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -X POST \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionReceipt",
    "params": ["0x..."],
    "id": 1
  }'

Response

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

eth_simulateV1

Simulates transactions using the latest flashblock state.

Request

curl https://sepolia-rpc-flashblocks.giwa.io \
  -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
  }'

Response

{
  "jsonrpc": "2.0",
  "result": [
    {
      "calls": [
        {
          "status": "0x1",
          "gasUsed": "0x1234",
          "returnData": "0x"
        }
      ]
    }
  ],
  "id": 1
}

Learn more

Check out the OP Stack developer docs for further details.