Layer 2 (L2) networks share security with mainnet by publishing transaction data on Layer 1 (L1). As a result, L2 users still pay some L1 gas costs when executing transactions. Since L1 gas can be >25,000x more expensive than L2 gas, paying for L1 calldata dominates L2 transaction costs. With custom contracts that use less calldata than standard methods we significantly reduced transaction costs for users."
Dir. of Engineering