In this work two indexing approaches are presented for case-based reasoning. The first is a hybrid technique which uses a combination of a matrix and a tree structure to solve problems. The second is based solely on the tree structure and never uses the matrix. The techniques are evaluated in terms of their competency and efficiency with respect to nearest neighbor retrieval. Both approaches provide efficiency gains in the region of 20 fold with only a slight loss in competency, as averaged across all case-bases tested. It is argued that these approaches are appealing due to their simplicity, competency, efficiency and ability to provide real time maintenance of retrieval knowledge in case-based reasoning.