August 31, 2019 Vitalik Buterin highlights an emerging class of hybrid Layer 2 scaling approaches.

In the proposed architecture, L2 data is published but not verified on-chain, and instead subject to a challenge period before confirmation. The main chain verifies data availability, but not block validity. An early example of this approach, ZK Rollup, would increase the Ethereum network’s transaction capacity to 500 TPS. This approach is in contrast to existing Ethereum Layer 2 networks focusing specifically on payments, such as Celer or Plasma Cash.