KoinlyticsRollups execute transactions off-chain and post a compressed record to Ethereum. Two families do this in fundamentally different ways.
Optimistic rollups
Assume every batch is valid. Post it to L1. Anyone can dispute within a 7-day challenge window by submitting a fraud proof. If nobody disputes, batch finalizes. If a fraud proof succeeds, the batch is rolled back and the sequencer is slashed. Arbitrum, Optimism, and Base are optimistic.
ZK rollups
Prove every batch mathematically before posting. A validity proof (usually a SNARK or STARK) says "I ran these transactions correctly." The L1 contract only accepts batches with a valid proof. No challenge window needed. Withdrawals are as fast as the next proof, often minutes. zkSync, StarkNet, Linea, Scroll, and Polygon zkEVM are ZK.
Withdrawal delay
- Optimistic: 7 days official. Third-party bridges (Across, Hop) let you cut this to minutes for a fee.
- ZK: batches finalize in minutes to hours. Native withdrawals are fast.
Cost per transaction
Both use blobs (EIP-4844) since March 2024. Optimistic and ZK L2 fees are within an order of magnitude for basic swaps: $0.005 to $0.05. ZK rollups pay a proving cost that shows up as higher fees for complex transactions.
Where each wins
- Optimistic wins on tooling parity. Full EVM equivalence, every Ethereum dev tool works day one.
- ZK wins on finality and privacy. No 7-day trust window, and proofs enable privacy features that fraud proofs cannot.
- ZK wins as the L2 count grows. A ZK proof of "this L2 is correct" is a fixed size regardless of how many transactions it batches.
The endgame
Most bets: ZK rollups will eventually dominate for new deployments once proving costs collapse further and EVM equivalence catches up (StarkNet and zkSync both shipped Type-1 or near-Type-1 zkEVMs in 2025). Optimistic incumbents (Arbitrum, Base) will migrate their proof system to ZK under the hood without users noticing.