Shared Sequencers

In most current Layer 2 rollups, there is a single entity called a "sequencer" that receives transactions from users, orders them, and submits them to the main chain (Layer 1). Because most rollups currently run their own private sequencer, they are effectively centralized; the rollup team could technically censor a user or extract value (MEV) by reordering transactions. A shared sequencer replaces this single entity with a decentralized network of nodes that provide sequencing services for many different rollups simultaneously.

The biggest advantage of shared sequencers is "atomic interoperability." If two different rollups use the same shared sequencer, it becomes possible to execute a transaction that spans both chains in a single step. For example, you could swap a token on Rollup A for a token on Rollup B without waiting for a slow bridge process, because the shared sequencer can guarantee that both parts of the swap happen together. This reduces the "fragmentation" that currently plagues the Layer 2 ecosystem, where liquidity is split across dozens of different isolated networks.

For investors, shared sequencers are a key piece of "middleman" infrastructure. They represent a new layer in the stack that can capture value through transaction fees and MEV. Projects like Espresso and Astria are leading this space. However, using a shared sequencer means a rollup is giving up some control over its own transaction ordering, which can impact its ability to earn revenue from its own MEV. Investors should watch for which Layer 2s choose to decentralize their sequencing and whether shared networks become the industry standard.