I'm not referring to single meta_key look ups but was referring to non-indexed key + value queries on large wp_postmeta tables. Eventually a developer will need

I'm not referring to single meta_key look ups but was referring to non-indexed key + value queries on large wp_postmeta tables. Eventually a developer will need to do a meta_key + meta_value look up in some query which will tank performance on large table sizes. With plugins like Advanced Custom Fields, the wp_postmeta table can drastically increase in size and a developer can quickly fire off dozens of non-indexed key + value queries in one request. Given JSON support in MySQL, Postgresql, et al, there is no need to not migrate away from such a poor schema. Source: also work in the media world and have large WP installations in my charge. WP is a resource burden.