Since the BLAST databases are fetched from the NCBI, downloads are faster if the instance runs in a region that is geographically close to NCBI. NCBI is located in the east coast of North America.

For AWS, us-east-1 (N. Virginia) is the closest region, so for optimal download performance, please consider starting your instance in that region. You can find a list of available AWS regions here.

In other cases, such as us-west-1 (N. California) and eu-west-1 (Ireland), downloading the BLAST databases can take a few hours.