Layer 2s & rollups
Rollups execute transactions off Ethereum and post proofs back on-chain — cheaper fees, same security.
> The scaling problem
Ethereum's base layer processes ~15 transactions per second. That's fine for high-value settlement but useless for everyday payments or gaming. Layer 2s (L2s) are separate chains that batch thousands of transactions and settle a compressed proof back to Ethereum.
> Optimistic vs ZK
Optimistic rollups (Optimism, Arbitrum, Base) assume transactions are valid and allow challenges during a 7-day window. ZK rollups (zkSync, Starknet, Linea) submit cryptographic validity proofs — no waiting period, but heavier cryptography.
> Why it matters
L2 fees are typically 10-100x cheaper than mainnet. Most active DeFi, NFT trading, and consumer apps have migrated to L2s. Ethereum's roadmap treats L2s as the primary user surface and the base layer as a settlement anchor.