An online storage system receives a plurality of documents to be stored in a directory. The storage system stores document data from each document in a document database. The storage system generates an entry for each document in an entry table and indexes the documents stored in the directory. The storage system samples a subset of the plurality of documents assigned to the directory in a directory index to determine a sampled subset of the plurality of documents. The storage system indexes the sampled subset in a directory index. The storage system can receive a request, from a client device, to view the indexed documents in the directory. Responsive to the request, the storage system presents the indexed documents in the directory retrieved from the directory index.