– Optimistic Rollups like Arbitrum and Optimism use a dispute period of 7 days to ensure transaction truthfulness. Transactions happen on a layer 2 network where they are grouped up before being passed to the layer 1 chain. Consequently, Optimistic Rollups’ 7 day process can slow down the pace of withdrawals. Developers have on occasion claimed that the older and familiar implementation of Optimistic Rollups makes for a relatively easier implementation relative to Zero-Knowledge (ZK) Rollups.

– ZK Rollups use complex mathematics and computer science rather than a dispute period to ensure that compiled and posted transactions sent to the layer 1 chain are accurate by creating a cryptographic message that proves a statement’s truth. In taking this route, Zero Knowledge Rollups remove the need for trust in human recognition of errors and reduce the potential for malicious behavior in transactions. This shifted reliance on computation has the possibility to compress transaction windows and speed up the overall process.

While ZK Rollups may seem the more efficient and logical route, at the moment the primary use case is to send relatively simple transactions like the movement of tokens between wallets, while the reliability of complex operations such as those used in most smart contract applications is still being developed.

The ZK approach to data compression incorporates a greater degree of privacy by design because of the trust-less nature of the setup and lack of a 7 day ‘arbitration’ period. Coupled with expanding capabilities of ZK Rollups via the advent of Zero-Knowledge Ethereum Virtual Machine (zkEVM) and early implementation by groups like Polygon, ZK Rollups appear slated to become the dominant rollup solution in the near future.