What is a based rollup?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 5 min
In short
A based rollup delegates transaction ordering to layer 1 block proposers instead of running its own sequencer. Because no single operator sequences, the outage and censorship problems tied to that role go away. In exchange, block timing and fee behaviour are bound to layer 1.
Key points
- Ordering is delegated to layer 1 block proposers
- Avoids the outage and censorship risks of a dedicated sequencer
- Block timing is tied to layer 1's cadence
- Changes how confirmation feels from the user's side
Definition
A rollup with no dedicated sequencer, in which layer 1 block proposers determine the ordering of layer 2 transactions.
In a typical rollup, a sequencer run by the operating team orders transactions. That is fast, but if the sequencer stops, transactions stall, and excluding particular transactions is technically possible. A based rollup hands that role to layer 1 proposers instead.
Layer 1 proposers already order transactions when building layer 1 blocks. Including the layer 2's transactions in that process means the layer 2 needs no sequencer of its own, and it inherits layer 1's censorship resistance and liveness properties directly.
The cost is responsiveness. Structurally, it is hard to promise an ordering the instant a transaction arrives, the way a dedicated sequencer can, so confirmation follows layer 1's block cadence. Pre-confirmation schemes to compensate are an area of research, and their designs and assumptions differ by project.
Watch out for
- · Confirmation follows layer 1's block cadence and can take longer than with a dedicated sequencer
- · If pre-confirmations are offered, check who is actually backing that promise
- · Congestion on layer 1 is felt directly