The article from Circle Internet Financial delves into four key authorization flows for USDC smart contract interactions using Circle SDK on EVM-compatible chains, highlighting the programmability of USDC. It covers traditional approval methods like "approve" and gasless alternatives such as "permit" (EIP 2612) and "transferWithAuthorization" (EIP 3009), as well as the use of "Permit2," an external Uniswap contract not part of the USDC token contract, for unified approvals across multiple tokens. Each method is explored in terms of how allowances are managed and where they are stored, with practical applications for different user experiences, from recurring transactions to gasless checkouts and unified token management. The text serves as a guide for developers to choose the appropriate authorization flow that aligns with their application's user experience and security objectives, suggesting the use of Circle Developer Controlled Wallets SDK for implementation.