The subject matter described herein relates to protecting in-flight transaction requests, where a client device is connected via at least two application servers to a backend server device that is capable of processing redundant transaction requests originated by the client device. A first instance of a transaction request identified by a transaction identifier is received at the backend server device. The first instance of the transaction request is processed and a transaction response is sent to the client device. The transaction response identified by the transaction identifier is saved in a cache. If a subsequent instance of the transaction request is received, the cached transaction response is sent to the client device.