In the race to scale Ethereum, Rollup technology remains the cornerstone. From Optimistic Rollups to Zero-Knowledge Rollups, each solution offers trade-offs. In March 2023, Ethereum researcher Justin Drake introduced a new paradigm—Based Rollups—aimed at addressing the centralization, censorship, and complexity issues inherent in existing sequencer designs.
Limitations of Optimistic and ZK Rollups
Traditional rollups come in two main flavors: Optimistic Rollups assume transactions are valid by default, relying on fraud proofs to ensure security, but suffer from long withdrawal delays. ZK Rollups use cryptographic proofs (SNARKs/STARKs) to provide validity proofs, offering faster finality. However, both rely on their own sequencers to order transactions, introducing risks of single points of failure, censorship, and complex token-economic incentives.
How Based Rollups Work
The key innovation of Based Rollups lies in moving sequencing to Ethereum's Layer1 infrastructure. Instead of using a separate sequencer, Based Rollups leverage the existing L1 searchers, builders, and proposers to order and include rollup transactions in L1 blocks. This permissionless design means anyone with access to the rollup's mempool can participate in sequencing, dramatically increasing decentralization.
The transaction lifecycle involves four steps:
- Step 1: L2 searchers bundle user transactions into batches.
- Step 2: L1 searchers and L2 block builders collaborate to sequence transactions and create complete L2 blocks.
- Step 3: L1 searchers submit these full L2 blocks to L1 block builders.
- Step 4: L1 block builders pass the L1 blocks (containing L2 data) to L1 validators for processing like any other L1 transaction.
This process is fully permissionless—any rollup block can be included in an L1 block without special permissions. It ensures that Ethereum's security guarantees extend seamlessly to Layer2 while eliminating the gas overhead of sequencer signature verification.
Pre-Confirmations: Faster User Experience
Based Rollups introduce pre-confirmations: transactions are confirmed before they are included on-chain, drastically reducing latency. To enforce this, proposers face increased slashing penalties if they fail to include pre-confirmed transactions. This mechanism balances speed with security accountability.
Advantages and Challenges
Key advantages include:
- Enhanced decentralization: Relies on L1 infrastructure rather than a single sequencer.
- High reliability, minimal downtime: L1 validators guarantee liveness.
- Reduced costs: No gas overhead from sequencer signature verification.
- Simpler architecture: Reuses existing L1 tech stack, avoiding complex consensus mechanisms.
Main limitations include:
- Loss of MEV revenue: Maximal Extractable Value is captured by L1 instead of the rollup.
- Reduced sequencing flexibility: Cannot customize order logic for maximum efficiency.
- Scalability bounded by L1: Throughput is limited by L1 block space and time.
Despite these trade-offs, Ethereum co-founder Vitalik Buterin has stated that starting next year he will only publicly mention Stage 1+ Layer2s. Currently, only Arbitrum and Optimism among Optimistic Rollups have reached Stage 1. Based Rollups share the same fraud-proof mechanism as their optimistic cousins, allowing them to inherit the best of existing champions while adding a more decentralized sequencing layer.
Who Is Building Based Rollups?
Several projects are actively exploring this space: Taiko, Espresso, Fairblock, Sorella, and Chainbound. They represent the frontier of Layer2 scaling, promising a future where Ethereum's security is fully leveraged for high-performance decentralized applications.
In summary, Based Rollups represent a compelling compromise between decentralization, security, and cost. By returning sequencing power to the L1, they simplify the stack and align incentives with Ethereum's core ethos. While they cede MEV revenue and some flexibility, their architectural elegance and trust minimization could make them a cornerstone of Ethereum's scaling roadmap.