Troubleshooting Drush with Acquia Dev Desktop

Scenario: large Drupal 7 site where cache is extremely slow or fails to clear…

drush cc all

…and eventually PHP runs out of memory (“cannot allocate”).

Check Drush is using the correct version of PHP, it may not be – use drush status or, more simply: drush php

To fix:

$ which drush
/Applications/DevDesktop/tools/drush

$ vim /Applications/DevDesktop/tools/drush

# edit the PHP version: [ -z "$PHP_ID" ] && PHP_ID=php7_1