Scroll vs Base: five myths about zkEVM sequencer decentralization

Finality speed and the 7-day window

Optimistic rollups like Base and Optimism rely on a seven-day challenge window for native withdrawals to Ethereum. This period exists so any participant can submit a fraud proof to dispute an invalid state transition. ZK rollups like Scroll use mathematical validity proofs to settle transactions, which removes this specific seven-day settlement period. While ZK rollups offer faster finality than Optimistic counterparts, users still face delays while the rollup closes a batch, generates a proof, and waits for the final Ethereum confirmation on the base layer after the batch reaches the L1 contract. A typical Scroll batch contains approximately 20 blocks or 200 transactions and takes about 50 minutes to finalize on L1. Following the Ethereum Dencun upgrade in March 2024, Optimistic rollups achieved a 90-99% reduction in fees. Does the reduction in withdrawal time compensate for the computational intensity of ZK proof generation?

The fallacy of Stage 1 decentralization

Base reached Stage 1 in April 2025 through the implementation of permissionless fault proofs. This milestone did not decentralize the sequencer, as Coinbase continues to operate the sole sequencer for the network. A single operator controlling transaction ordering creates risks of censorship, MEV extraction, and liveness failure. The February 2025 Base outage demonstrated how a single-operator sequencer creates a single point of failure. You likely assume that reaching a higher stage of maturity implies a decentralized sequencer, but these two milestones do not overlap. Base generated over $75 million in sequencer revenue through 2025, which shows the massive economic stakes of sequencer control. The regulatory pressure on sequencer operators remains high, as frameworks like the U.S. BSA may classify them as money transmitters. Linea also demonstrated sequencer vulnerability when it paused its sequencer in June 2024 for one hour to censor attacker addresses following a Velocore DEX exploit. Arbitrum currently qualifies as a Stage 1 rollup, leading Optimism, which remains at Stage 0.

The unfulfilled sequencer roadmap

Most major Ethereum L2s still run a centralized sequencer in 2026. Production-grade sequencer decentralization for most major L2s remains 12 to 18 months away, which means most networks will not achieve this until late 2026 or 2027. Optimism operates a single centralized sequencer run by the Optimism Foundation. While Optimism targets integration with shared sequencing infrastructure in 2026, it remains fully centralized today.

Espresso Systems leads the shared sequencing market with Mainnet 0, which uses a permissioned set of approximately 100 geographically distributed nodes. This network follows the HotShot consensus and has processed over 20 million transactions. In contrast, the Astria project shut down in December 2025. Arbitrum remains one level ahead of Optimism in its efforts to expand the validator set and implement fraud proofs. The market focus remains on Type 2 zkEVMs, which aim for bytecode-level equivalence to allow for the migration of Ethereum dApps without code changes.