Methods, apparatus and computer program product for generating tiered search index fields based on a divided group-based communication data corpus in a group-based communication platform are described herein. In some embodiments, the system provides for receiving a group-based communication data corpus, generating a retrieval score, and assigning each group-based communication data object associated with a retrieval score. Each group-based communication data object may meet or exceed a retrieval score threshold of a high retrieval probability corpus. Each group-based communication data object associated with a retrieval score below the retrieval score threshold may be assigned to a low retrieval probability corpus. High and a low retrieval probability search index fields may be generated and associated with the high and low retrieval probability corpus.