Rollup
Definition
A rollup is a Layer 2 scaling solution that executes transactions off the main Ethereum chain but posts transaction data back to Layer 1 for security. There are two main types: Optimistic Rollups (Optimism, Arbitrum) assume transactions are valid unless challenged, while ZK-Rollups (zkSync, StarkNet) use zero-knowledge proofs to verify transactions mathematically.
Example
Arbitrum is an Optimistic Rollup that processes transactions at a fraction of Ethereum mainnet gas costs while inheriting Ethereum's security guarantees.
Risks to Consider
- Bridge risk when moving assets
- Sequencer centralization
- Withdrawal delays (Optimistic)
Common Questions
What's the difference between Optimistic and ZK rollups?
Optimistic Rollups assume validity and allow fraud proofs within a challenge period (typically 7 days). ZK-Rollups prove validity mathematically with zero-knowledge proofs, enabling faster finality but with more complex technology.