There are some new drush Drupal 8 commands that are critical to updating your site. The big new one here, is "drush entitity-updates". Which should be initiated AFTER "drush updb".
Otherwise, if you check your Drupal 8 "Status Report" you may get an error showing "Entity/field definitions: Mismatched entity and/or field definitions"--which won't be apparent, unless you check the Status Report.
So here goes...
Clear all cashes (no longer "drush cc all"):
Update the database (this is still the same, however, you won't be done here):
After running "drush updb", you should next run entity updates command:
BONUS: clear cache directly through the database.
TRUNCATE TABLE cache; TRUNCATE TABLE cache_block; TRUNCATE TABLE cache_bootstrap; TRUNCATE TABLE cache_field; TRUNCATE TABLE cache_filter; TRUNCATE TABLE cache_form; TRUNCATE TABLE cache_image; TRUNCATE TABLE cache_menu; TRUNCATE TABLE cache_page; TRUNCATE TABLE cache_path; TRUNCATE TABLE cache_token; TRUNCATE TABLE cache_update; TRUNCATE TABLE cache_views;