Methods, systems, and apparatus, including computer programs encoded on computer storage media, for using reactive programming operators to implement resource pooling. One of the methods includes receiving a first request, from a client application, for a poolable object in a resource pool and maintained by a resource pool manager, wherein the request indicates an operation mode specifying how the resource pool manager should release the poolable object back into the resource pool; generating a plurality of reactive programming operators comprising a poolable object listener publisher and a subscriber that is configured to subscribe to the poolable object listener publisher; evaluating the reactive programming operators in an upstream subscription ordering of the reactive programming operators to obtain a poolable object from the resource pool; and releasing the poolable object back to the resource pool according to the operation mode of the request.