5. The method of claim 1 , wherein the step of indexing the selected proper subset of replicas includes the steps of: the computer determining index updates by determining keyword-to-replica mappings; and the computer generating the unified content index based on the index updates.
5. The method of claim 1 , wherein the step of indexing the selected proper subset of replicas includes the steps of: the computer determining index updates by determining keyword-to-replica mappings; and the computer generating the unified content index based on the index updates. 6. The method of claim 5 , wherein the step of determining the index updates includes the steps of: the computer determining index expectation scores for respective replicas in the selected proper subset of replicas; and the computer sorting the selected proper subset of replicas based in part on the index expectation scores for the respective replicas.