> For the complete documentation index, see [llms.txt](https://spire-docs.gitbook.io/spire/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://spire-docs.gitbook.io/spire/based-stack/traditional-shared-sequencing.md).
# Traditional shared sequencing
We recognize that significant effort has been made on traditional shared sequencers (shared sequencers that are not “based”).
> One valuable feature of the Based Stack is that appchains can still reap the benefits of shared sequencing with other L2s.
We implement a design called [Forward Based Sequencing](https://hackmd.io/@mteam/forward-based-sequencing), which gives shared sequencers (acting as forward sequencers) the ability to influence block production without a distinct monopoly. This enables shared sequencers to provide composability between Spire based appchains and other non-based rollups, especially when paired with execution preconfirmations.
{% hint style="info" %}
Execution preconfirmations allow forward sequencers to get (collateral-backed) execution guarantees that can be used to approximate atomic execution. We call this “optimistic atomic execution.”
{% endhint %}
One important thing to note is that this design could theoretically be used in any rollup with an L1 escape hatch with a low wait period. In the Based Stack, we take this primitive to the next level by introducing forward sequencers as “first-class citizens” in block production by focusing on gas efficiency, practical technical integrations with shared sequencers, and docs for integration.
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