Ethereum’s layer‑2 ecosystem carries a technical contradiction seldom addressed directly. Rollups are presented as scalability solutions that inherit the security of the base layer, yet most operate with a centralized sequencer that introduces a single point of trust. A sole operator decides transaction order, can censor addresses and captures the extractable value generated on the network. Users accept that architecture in exchange for fast confirmations and low fees, assuming that assets remain protected by forced‑exit mechanisms to L1. The based rollup proposal removes that trade‑off by shifting the sequencing function directly to Ethereum validators.
Optimistic and ZK rollups in production —Arbitrum, Optimism, Base, zkSync Era— depend on a sequencer node that bundles transactions, orders them and posts data to Ethereum. That node provides soft confirmations in milliseconds, but concentrates ordering power. The sequencer can extract MEV through reordering, insertion or exclusion of transactions, with no real‑time accountability mechanism. If the sequencer stops operating, the network halts from a user perspective, even though the rollup logic permits forced inclusion via L1. That forced inclusion remains slow and expensive, discouraging its use.
Decentralized sequencer networks and shared sequencers have been proposed as alternatives. Those solutions add an extra consensus layer, a staking token and separate infrastructure that replicates, on a smaller scale, Ethereum’s validation model. The result is an increase in system complexity and a trust model that remains external to the main chain. Based rollups take a different path: they eliminate the independent sequencer role entirely.
Precise definition of a based rollup
A based rollup is a rollup whose sequencing is determined by the L1 proposer assigned to each slot. The layer‑2 network does not elect its own sequencer or run a validator set; instead, it uses the proposer schedule of the Beacon Chain. The canonical L2 block is whatever block the Ethereum proposer includes within its L1 block, provided it respects the rollup’s state transition rules.
That definition carries immediate consequences. Sequencer decentralization matches that of Ethereum’s consensus layer, without the need to coordinate a new set of participants. No extra token or standalone consensus protocol is introduced. Censorship resistance of the rollup aligns with that of the base layer: if a proposer omits an L2 transaction, a future proposer can include it, because the rollup’s state machine derives its history deterministically from data posted to L1.
Block building mechanics and forced inclusion
The process integrates into Ethereum’s block production dynamics. In each 12‑second slot, the validator selected as proposer holds the right to propose the next L1 block. If that validator also acts as sequencer for the based rollup, it will include an L2 block within the data payload of its L1 block, typically as calldata or blobs. Transaction execution and L2 block construction need not be performed directly by the proposer. They can be delegated to specialized builders that compete to offer the L2 block with the highest MEV value, in a scheme analogous to MEV‑Boost. The proposer selects the most profitable proposal, includes it and signs it within its block.
The forced inclusion mechanism operates as a backstop guarantee. Any user can submit a transaction directly to the L1 mempool so that a future proposer incorporates it into the L2 block. If the current proposer censors certain operations, the transaction will be processed in a later slot without permission. Rollup transaction finality follows L1 finality timing, eliminating the assumption of an honest sequencer.
Based preconfirmations: speed without permanent centralization
The main objection to the design is latency. Confirmation at Ethereum’s slot time —12 seconds until inclusion and longer until finality— proves unacceptable for applications requiring immediate feedback. Research into based preconfirmations offers a solution without reintroducing a centralized sequencer.
The mechanism relies on the fact that the proposer schedule is known several slots in advance. A future proposer can bindingly commit to including a transaction with a specific order and resulting state. That commitment materializes as a signature that can be backed by the validator’s stake. If the proposer breaks the promise, it faces economic penalties, contingent upon the Ethereum protocol incorporating slashing conditions for preconfirmations. The user receives a confirmation with economic guarantees before the L1 block is proposed. Trust is placed in an operator with a limited window of action —a single slot— rather than in a permanent sequencer.
Eliminating the permanent sequencer produces three structural effects at the layer‑2 level.
First, architectural simplicity. A based rollup reduces the attack surface and governance burden. No sequencer set, staking token or leader‑election mechanism need to be managed. State derivation from L1 becomes the sole coordination mechanism.
Second, economic alignment between L1 and L2. MEV generated on the rollup flows to Ethereum proposers and, by extension, to ETH stakers. In the current model, layer‑2 MEV is captured by the centralized sequencer operator, who may internalize it or redistribute it according to arbitrary criteria. With a based rollup, that value strengthens the economic security of the base layer itself, reinforcing the entire ecosystem without additional redistribution mechanisms.
Third, synchronous composability is simplified. Because a single proposer orders L1 and based‑rollup transactions within a common time window, atomic cross‑domain operations become possible without bridges carrying extra trust assumptions. That property reduces liquidity fragmentation and cross‑chain contract complexity.
The first challenge is real‑time block building. The executor assembling the L2 block has a window of a few seconds before the proposer must seal the L1 block. For rollups with complex execution or large transaction volumes, that time constraint demands optimized builder infrastructure and possibly specialized hardware. The solution involves separating building from proposing, but builder competition must be liquid enough to prevent oligopoly formation.
The second challenge is cross‑domain MEV. A proposer that simultaneously controls ordering on L1 and on the based rollup can extract value through strategies that cross both layers, such as price manipulation on an L1 exchange based on privileged information about L2 transactions not yet public. Mitigation techniques include threshold encryption, forced temporal separation between transaction disclosure and execution, and ordering‑right auction mechanisms. Research in this area remains at an early stage.
The third challenge affects the business model of L2 teams. Rollups that operate a centralized sequencer earn direct revenue from MEV capture and from the margin between the cost of posting data to L1 and user fees. In a based rollup, the bulk of MEV is redirected to L1 proposers. Development teams will need to articulate alternative revenue sources, such as inclusion fees, block‑building services or subscription models for applications.
Current state of the technology
The reference based rollup on mainnet is Taiko, a ZK‑rollup that implements based sequencing from launch. Taiko delegates transaction ordering to Ethereum proposers and relies on validity proofs to guarantee state‑transition correctness. The team works on based preconfirmations to improve user experience, in collaboration with Spire Labs, which is developing a stack for based appchains.
Research at the Ethereum protocol level is also advancing. Proposals such as execution tickets and inclusion lists complement the based‑rollup design, by allowing proposers to commit to including certain transactions without long‑term censorship risk. Integrating those mechanisms with the consensus layer could formalize the role of proposers as universal temporary sequencers.
Ethereum’s layer‑2 architecture faces a decision that will define its decentralization profile for years ahead. Maintaining centralized sequencers means accepting single points of censorship and rent extraction, justified by a better user experience. Based rollups demonstrate that the trade‑off is avoidable. By delegating sequencing to existing validators, a system is obtained with censorship resistance equivalent to L1, coordination simplicity and a MEV flow that strengthens Ethereum’s security.
Practical viability depends on the development of efficient preconfirmations and a competitive builder ecosystem. Teams that commit to this model will need to reconfigure their revenue sources. For a sector pursuing credible neutrality and base‑layer alignment, based rollups represent a structural correction that removes one of the most persistent centralization vectors in the rollup ecosystem. The industry now has access to prototypes and research necessary to evaluate whether that correction becomes the design standard for layer 2s.
Be the first to comment