ZK Rollup

ZK rollups post cryptographic validity proofs to Layer 1 that the batch is correct, so they skip fraud proofs and challenge windows. SNARKs or STARKs produce a small proof that a computation ran correctly. L1 verifies the proof without re-executing the transactions. Verification is cheaper than proving, which is why the economics work: heavy off-chain proving, cheap on-chain checks.

Finality arrives once the proof lands. Security is cryptographic rather than a game of challengers. Scalability can improve as provers get faster. Costs remain. Proving is compute heavy. Full EVM compatibility inside circuits is hard. The stack is younger. ZkSync Era and StarkNet are general-purpose ZK rollups. Polygon zkEVM aims at full EVM equivalence.

Trading-focused rollups such as dYdX v3 and Loopring proved the model first. Many expect ZK rollups to be Ethereum's long-run scaling path as proving costs fall. The technology uses zero-knowledge proofs (SNARKs or STARKs) to create a compact proof that an arbitrary computation was performed correctly.

Benefits include major: instant finality once the proof is posted (no 7-day wait), stronger security guarantees (cryptographic rather than economic), and potentially better scalability as proof technology improves.

The challenges: ZK proof generation is computationally intensive and expensive; achieving full EVM compatibility in ZK circuits is technically difficult; and the technology is less mature. A ZK-rollup posts a validity proof with the batch. Ethereum checks the proof. It does not re-run every transaction.