Mechanism

The Shadow Sequencer serves as a decentralized network of nodes, leveraging CometBFT to achieve consensus on an ordered set of transactions, effectively functioning as a blockchain. Notably, the sequencer's standout characteristic lies in its mode of operation: it includes transactions without executing them, a process referred to as lazy sequencing.

Instead, it forwards these transactions to another execution engine, such as a rollup. This excludes transactions native to the sequencer itself, like token transfers within its chain. Transactions from any specific rollup are solely ordered on the sequencer but not executed within it.

Optionally, the sequencer can undertake the role of a validator, actively engaging in the generation and finalization of new blocks within the network.

In the infrastructure of the development cluster, Celestia serves as the data availability layer, acting as the ultimate repository for all data organized by the sequencer network. Once data is inscribed into Celestia, the transaction order attains finality. Consequently, when initializing a new rollup node, all requisite data is sourced from Celestia.

See the Celestia website for a more in depth introduction.