1. A method comprising: accessing a first set of values generated by a stateless constraint engine, wherein the first set of values are generated based upon a first set of inputs to the stateless constraint engine, wherein the first set of inputs indicates a first set of user selections during a product configuration, and a set of one or more rules applied by the stateless constraint engine; accessing a second set of values generated by the stateless constraint engine, wherein the second set of values are generated subsequent to generation of the first set of values, the second set of values are generated based upon a second set of inputs to the stateless constraint engine, the second set of inputs indicates a second set of user selections during the product configuration, and the second set of user selections is made subsequent to the first set of user selections and subsequent to generation of the first set of values; and validating the second set of values based upon a precondition and a postcondition, wherein the validating is performed by at least one processor, the precondition is dependent upon at least one value from the first set of values, and the postcondition is dependent upon at least one value from the second set of values.