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Ecosystem · medium

45. Layer 2s and Base

Rollups, calldata costs and cross-chain messaging.

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Optimistic rollups such as Base execute transactions off chain and post data to Ethereum, inheriting its security with a challenge window for withdrawals. Execution gas is cheap; posting data is the real cost, so smaller calldata means cheaper transactions.

solidity
// same Solidity, different chain id and RPC

Never assume L1 and L2 block times or timestamps match, and treat bridges as trusted components with their own risk.

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  1. 1. Where does an optimistic rollup post data?

  2. 2. What dominates L2 transaction cost?

  3. 3. Why is there a withdrawal delay?

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