Implementations of the disclosure describe an expandable index including pages that may store object records. The index may be divided into buckets, and each bucket may be associated with pages from a pool of unused pages shared by the buckets. A table or log may be used to maintain a dynamic list of all unused pages. It may also maintain a list of pages currently associated with buckets. As pages are linked to or unlinked from a bucket, the table or log may be updated to reflect that a page has been linked to a bucket or that a page that is no longer linked to a bucket belongs to the pool of unused pages. As additional storage media are added to the system, additional pages may be added to the pool of the expandable index for use by existing buckets without changing the number of buckets of the index.