> For the complete documentation index, see [llms.txt](https://docs.ethgas.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ethgas.com/overview/realtime-faqs.md).
# Realtime FAQs
## Realtime Block Building
How often are Realtime blocks produced?
Sub-slots are sequenced with a target timing of 200ms and require a 3-4 second window at the start of the block before the fast sequencing starts. This is due to the time it takes for the previous block's state to update/propagate.
Where there are two consecutive realtime (12-sec) blocks, the 200ms sub-slot sequencing happens continuously between the two blocks for a seamless experience.
Will the number of Realtime blocks per block always be the maximum?
Not always. Heavy execution in one interval may reduce time available for subsequent intervals. The REALTIME\_TIME setting is a target, not a strict guarantee.
Why isn't the Realtime block building always enabled?
When the validator assigned to the current slot hasn't delegated to us, the realtime block building will be disabled. See [Which Blocks are Realtime?](/overview/which-blocks-are-realtime.md) for more information.
How do you sort each sub-block in real time?
As we assemble every sub-block, we keep reordering simulated bundles/txs by their effective priority fee. So the highest-paying orders are always tried first at each sub-block.
Where are ETHGas Realtime builders located?
The ETHGas Realtime builders are located in `Tokyo AWS in Zone apne1-az4`
What are the Realtime Builder Public Keys?
Mainnet:
* `0x86f3ad359674f58ca09fbb9254d7a65251184b7326b948b6d8057a6d8d062b053e87cca4a74b75603aaac521048174f1`
Hoodi:
* `0x96b5d4d9f95043b84a541ae8ee38cf51621d8c965c7a9fbc41d75474facfd422bde5d45ce7f2d3a2491e37e5474d0125`
## Transactions
How do you set the gas fee for a Realtime block?
Calculating the required gas fee for Realtime blocks is the same as for any normal block when using the ETHGas Realtime RPC.
If you are not using the Realtime RPC, and therefore underpay the required gas fee, your transaction may not be included in the Realtime block.
Do large gas transactions get delayed?
High gas transactions can be included in any Realtime block with sufficient gas capacity. Placement is optimized by heuristics, but available gas decreases as transactions fill earlier Realtime blocks.
## High Availability and Safety
What happens if the Realtime builder fails?
Our ETHGas relay will fallback to a regular MEV-Boost block build (including pre-confirmation bundles).
Do Realtime blocks change the safety model of Ethereum?
No, each realtime block is validated by the same execution engine as normal blocks
Why do we need ETHGas Realtime block building?
ETHGas realtime blocks change how fast apps can respond on Ethereum. Instead of waiting for full block finality (12 secs), you get an early signal of inclusion, fast enough to make things like trading, gaming, or live dashboards feel instant. It also works with standard RPC methods and doesn't require any new setup.
How does ETHGas Realtime block building prevent MEV attacks?
As realtime blocks build and finalize a new sub-block roughly over 50-100ms, this leaves limited time for a searcher to see your transaction in the mempool and then exploit it. 100ms sub-blocks are expected to have about 91% less MEV.
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