> For the complete documentation index, see [llms.txt](https://docs.novarpc.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.novarpc.xyz/nova-rpc/where-is-nova-available/how-it-works-on-l2/nova-on-arbitrum.md).

# Nova on Arbitrum

* **Timeboost:** The first wave of centralized sequencers, such as those operated within Base and Arbitrum ecosystems, ordered transactions based on a first come first served (FCFS), and via optional priority fees.\
  \
  However, downsides to FCFS emerged in the form of increased network congestion from searchers spamming the network to take advantage of MEV opportunities. In response, Offchain Labs developed Timeboost – a transaction ordering policy which combines an express lane and an offchain auction to protect users from MEV and reduce network spam, whilst preserving fast block times. 

* **Kairos:** Built by the same team behind Nova, Kairos is a native integration with Arbitrum Timeboost that offers a streamlined path for searchers and other participants to access express-lane blockspace—without directly engaging in each round-level Timeboost auction. <br>


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