Cross-posting here since it is likely to be of interest. From BLAST product manager at NCBI:
RefSeq select offers a high-quality set of transcript and protein sequences for human and mouse; for prokaryotes, RefSeq select is the set of proteins annotated on RefSeq reference and representative genomes. You can now search these sets on the nucleotide and protein BLAST services. The new databases are 'RefSeq Select rna sequences' and 'RefSeq Select proteins'.
Searches against these more compact databases run faster and give search results that are better defined and easier to interpret. You can also download the pre-formatted refseq_select_rna and refseq_select_protein databases from the BLAST db FTP directory for use with a local BLAST installation. You can also get these databases on the Amazon and Google clouds with the BLAST+ Docker image. See the NCBI Insights post for additional details.