On April 12, 2022, Metis integrated a storage layer benefitting its rollup structure. Metis is now leading the L2 industry with the lowest gas costs of all L2s, while maintaining high security and data availability. Through leading innovation and evolution, L2Beat has reclassified Metis as an Optimistic Chain. In light of this label, the Metis community is reviewing the new classification, as the term “chain” does not accurately reflect the Metis L2 infrastructure. Metis continues to have a rollup structure while exploring the area between Plasma and Rollups. To avoid confusion within the industry, the Metis community is reviewing the new classification and is considering the term Smart L2 to best represent its architecture.

In light of major innovations continuing within the L2 industry, L2Beat recently announced the Optimistic Chain, a new classification category for L2s with data storage designs different from Optimistic Rollups, specifically referring to L2s hosting data off L1. The L2Beat label currently applies to Metis, upcoming AnyTrust chains from Arbitrum, as well as other L2s that rely on Celestia for data availability.

Through Metis’s leading innovation and upgrade, gas costs on Metis have witnessed significant reductions from around $2-$3 just a few months ago to current costs of $0.02 and $0.14 per swap (Source: L2fees.info). Metis is now the only L2 to meet Vitalik Buterin’s “truly acceptable” threshold of under $0.05 fee transactions.

What classifies Metis as a Smart L2 or Optimistic “Chain” versus an Optimistic Rollup?

After integrating its storage layer, Metis remains a L2 while reclassified due to differences in full data availability on L1 versus traditional Optimistic Rollups. By default, Metis only submits transaction commitments (in merkletree format) to L1 and makes the full transaction data available on MemoLabs decentralized storage, from which the validators can download and submit fraud proofs if necessary. Transaction data is thus “Optimistic” available and deterministically validated via merkletree verification onchain when the validator needs to conduct a fraud proof because either the state root is wrong according to the transaction data, or because the sequencer broke the data availability assumption, such as withholding the transaction data. In other words, transaction data is posted to L1 on a need-be basis, before a fraud proof can be posted. In this event, the required data is validated on-chain through data availability requests. The current method is a gap closing measure until dank sharding is available. Once dank sharding is available, Metis will continue to evolve and easily switch back to hosting full data availability on L1 without significantly increased gas costs.

By integrating a distributed storage layer with a rollup structure, Metis is leading L2 innovation by achieving low costs while maintaining high security and data availability. Metis encourages other L2s to fork Metis’s open source code to continue building a web3 world more accessible for all. Through a collaborative effort, the L2 industry will better evolve and succeed together.

Source: https://twitter.com/l2beatcom/status/1520425802332094464
Source: L2fees.info
Source: https://twitter.com/VitalikButerin/status/1521501499410587653?s=20&t=9yUkRWyGXaz4sZ0q7-xy5Q
Source: https://metisdao.medium.com/the-tech-journey-lower-gas-costs-storage-layer-on-metis-867ddcf6d381