Technical Concepts

Rollup

Layer 2 scaling solution that executes transactions off-chain while posting data to Layer 1

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.

What to check

Treat it as infrastructure: understand what it automates, what trust assumptions remain, and how failures propagate. The main checks are: Bridge risk when moving assets; Sequencer centralization; Withdrawal delays (Optimistic).

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.

What does Rollup mean in DeFi?

Rollup means Layer 2 scaling solution that executes transactions off-chain while posting data to Layer 1. The useful question is not only the definition, but how the mechanism changes risk, return, liquidity, or governance for the user.

How is Rollup used in practice?

A practical example: Arbitrum is an Optimistic Rollup that processes transactions at a fraction of Ethereum mainnet gas costs while inheriting Ethereum's security guarantees.