LAYER 2 NETWORKS & SCALING
Plain English
Ethereum is slow and expensive when congested — sometimes costing $50+ to make a simple trade. Layer 2 networks (Arbitrum, Optimism, Base, Polygon) sit on top of Ethereum and process transactions much faster and cheaper, then settle the results back to Ethereum for security. They're where most DeFi activity now happens.
Going deeper
Layer 2 (L2) networks are scaling solutions built on top of Layer 1 blockchains (primarily Ethereum). They process transactions off the main chain to increase throughput and reduce fees, while inheriting Ethereum's security. Two main types: (1) Optimistic Rollups (Arbitrum, Optimism, Base) — assume transactions are valid by default and use a fraud-proof window (7 days) for challenges. Fees: 10-100x cheaper than Ethereum mainnet. (2) ZK-Rollups (zkSync, StarkNet, Polygon zkEVM) — use zero-knowledge proofs to cryptographically verify transaction batches instantly. More secure but more complex to build on. Key L2s: Arbitrum (largest DeFi TVL among L2s), Base (Coinbase's L2 — tied to Coinbase's user base), Optimism (OP token governance), Polygon (widely used for gaming and enterprise). Bridging: moving assets from Ethereum to an L2 requires a bridge transaction (takes minutes to hours). Moving back from Optimistic Rollups takes 7 days without a fast bridge service.
Examples
Fee Comparison
Ethereum mainnet: simple token swap costs $15–$50 in gas. Same swap on Arbitrum: $0.05–$0.30. Arbitrum processes the transaction in 1-2 seconds vs. 12-15 seconds on mainnet. The fee difference makes DeFi viable for smaller wallets — $500 trades that would have been eaten alive by gas fees are now practical.
Base's Explosive Growth
Coinbase launched Base (their own L2) in 2023. Within 6 months, Base had over $2B in TVL and was processing more daily transactions than Ethereum mainnet. The reason: Coinbase has millions of users who can bridge funds from their exchange account to Base with one click — far lower friction than other L2s.