Flashblocks is live on Chainstack: even faster Base RPC

Flashblocks is now live on Chainstack for Base Mainnet and Testnet Sepolia endpoints, bringing near-instant transaction signals that improve responsiveness. Built directly into Base, Flashblocks reduces effective confirmation time from 2 seconds to 200ms by streaming partial block updates before full block finality. 

On Base, a standard transaction takes ~2 seconds to confirm. That’s fast by Layer 2 standards, but for real-time low-latency trading, onchain games, and time-sensitive user flows, those two seconds can still feel like a delay.

Flashblocks, a transaction preconfirmation feature developed by Flashbots, introduces “partial blocks” that stream ahead of each new seal. Flashblocks is now fully supported on Chainstack Base Mainnet and Sepolia endpoints. If you’re a builder working on low-latency infrastructure, Flashblocks gives you access to ultra-fast preconfirmation signals, providing transaction feedback in as little as 200 milliseconds.

In this post, we’ll cover what Flashblocks is, how it works, where it helps, and show code examples using JSON-RPC and curl to help you get started.

What is Flashblocks on Base?

Flashblocks is a feature on Base that introduces low-latency block previews by streaming committed transactions as they’re added to the block-in-progress. Instead of waiting for full block finality, apps can access an early view of the next block that reflects transactions already included by the builder.

Each Flashblock contains transactions that have already been executed and committed by the builder as part of the in-progress block. This gives devs a low-latency signal that a transaction is already included, before the full 2-second block is finalized on-chain.

The mechanism is compatible with existing Ethereum JSON-RPC methods. Calls like eth_getBlockByNumber with the pending tag will return the current Flashblock. Others, like eth_getTransactionReceipt and eth_getTransactionCount, also reflect the latest Flashblock state.

Benefits of Flashblocks on Base

Flashblocks makes confirmations faster, but most importantly, it gives you better ways to build. Here’s what changes when you’re using Base RPC endpoint by Chainstack.

Get faster transaction signals

With Flashblocks, your app doesn’t need to wait two full seconds to update the UI. You get an early signal that a transaction is already included, even before the full block is finalized. That’s a big deal for anything time-sensitive: swaps, games, bots, or even a simple onboarding flow.

Low-latency RPC access, globally distributed

Chainstack Global Nodes for Base are optimized for intensive traffic. We route requests through the closest available region, whether that’s the US, EU, or Asia, and serve responses from high-performance nodes.

That means even when network traffic spikes, your app stays fast.

# Example: Fetch the latest Flashblock (pending block) via Chainstack Base RPC

curl -X POST <YOUR_CHAINSTACK_BASE_RPC_URL> \\

-H "Content-Type: application/json" \\

-d '{

"jsonrpc": "2.0",

"id": 1,

"method": "eth_getBlockByNumber",

"params": ["pending", false]

}'

Works with standard Ethereum RPC methods

Flashblocks works with standard RPC methods available on Base. Just use the “pending” tag with:

• eth_getBlockByNumber
• eth_getTransactionReceipt
• eth_getBalance
• eth_getTransactionCount

You’ll get fresher data, streamed from the latest Flashblock, without touching your existing tools.

Getting started with Flashblocks on Base via Chainstack

1. Create a Base RPC endpoint on Chainstack Flashblocks is currently supported on Base Mainnet and Testnet Sepolia. If you already have a Chainstack Base RPC endpoint on a supported node type, it’s Flashblocks-ready by default. You can create new endpoints in just a few clicks.
2. Connect your app, script, or tool Use your Chainstack RPC URL in your web3 app, wallet, script, or curl requests. All standard Ethereum JSON-RPC methods are supported, including the enhancements Flashblocks introduces.
3. Use Flashblocks features with standard RPC methods There are no new SDKs or complex integrations. You can start using the “pending” tag with methods like eth_getBlockByNumber, eth_getBalance, or eth_getTransactionCount to access real-time blockchain data.

Flashblocks on Chainstack unlocks near-instant confirmations, ideal for anything time-sensitive.

Conclusion

Flashblocks changes how fast apps can respond on Base. Instead of waiting for full block finality, you get an early signal of inclusion, fast enough to make things like trading, gaming, or live dashboards feel instant.

It works with standard RPC methods and doesn’t require any new setup. If you’re using a Chainstack Base RPC Mainnet or Testnet Sepolia endpoint on a supported node type, you’re already good to go.