> ## Documentation Index
> Fetch the complete documentation index at: https://docs.chainstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Chainstack updates: May 18, 2026

> Flashblocks on Optimism is live on every Chainstack Optimism mainnet node, with 250ms preconfirmations via standard JSON-RPC calls with the pending block tag.

**Protocols**. **Flashblocks on Optimism** is live on every Chainstack [Optimism](https://chainstack.com/build-better-with-optimism/) mainnet node. The Optimism sequencer streams Flashblocks every 250ms, and Chainstack Optimism nodes expose the preconfirmation state through standard JSON-RPC calls with the `pending` block tag — `eth_getBlockByNumber`, `eth_call`, `eth_getBalance`, `eth_getTransactionCount`, `eth_getCode`, `eth_getStorageAt`, `eth_estimateGas` — plus `eth_getTransactionReceipt`, `eth_getTransactionByHash`, and `eth_sendRawTransactionSync` for preconfirmed transactions.

See [Flashblocks on Optimism](/docs/flashblocks-on-optimism) for the full guide, including the Optimism vs. Base differences, performance expectations, and a verification snippet.