Queries go directly to on-chain contracts via public RPC endpoints. USDT: Ethereum, Tron, Avalanche, Solana, Aptos, TON. USDC: Ethereum, Arbitrum, Base, Optimism, Polygon, Avalanche, HyperEVM, Solana, Aptos, Sui. Aptos/Sui addresses (0x + 64 hex) are checked on both chains simultaneously.