Systems and methods of rate limiting are disclosed herein. In some example embodiments, a rate limiter service receives a request from an online application to access an online resource, and the rate limiter service transmits an indication of the request to a back end system, and an enforcement decision corresponding to the online resource is received from the back end system, with the enforcement decision comprising an instruction to either permit or deny access to the online resource, and the receiving of the enforcement decision from the back end system being performed asynchronously with the receiving of the request and the transmitting of the indication. In some example embodiments, the enforcement decision received from the back end system is stored, the stored enforcement decision is accessed in response to the receiving of the request, and the request is responded to using the accessed enforcement decision.