Various methods, apparatus, and systems are disclosed for calculating a fee linked to an online financial transaction, with improved flexibility and availability through caching and refreshing of fee calculation data. In one embodiment, a method includes extracting fee calculation data into a data cache associated with control data that is updated in response to refreshing of the data cache; receiving a fee calculation request linked to an online transaction associated with a fee type, a country code, and a client identifier; and then selecting, by looking up the data cache, a base fee from either a default fee determined by the fee type and the country code or from an overriding fee associated with the client identifier. The method further includes calculating a transaction fee for the online transaction based at least in part on the base fee; and verifying the control data to transmit the calculated transaction fee.