1. A method for load balancing in a server cluster comprising: configuring a load management application to use a load balancing decision function selected from a plurality of load balancing decision functions, wherein the plurality of load balancing decision functions comprises a default load balancing decision function and a custom load balancing decision function, wherein the default load balancing decision function is any load balancing decision function that is part of the load management application when the load management application is sent to a customer using the server cluster, wherein the custom load balancing decision function is created by a user, associated with the customer, for the server cluster, wherein the user creates the custom load balancing decision function by creating a method in a programming language, wherein the custom load balancing decision function implements a first application programming interface (API) specified by the load management application, and wherein the custom load balancing decision is not part of the load management application; receiving a request in the server cluster; selecting, for the request, a request handler from a plurality of request handlers by: performing, by the load management application, a method call on the custom load balancing decision function according to the first API, wherein the method call comprises a request attribute of the request; selecting, by the custom load balancing decision function, the request handler to process the request based on the request attribute; and receiving, by the load management application from the custom load balancing decision function, an identifier of the request handler in response to the method call; and transmitting, by the load management application, the request to the request handler.