How to clear caches on a busy drupal Site.

While clearing caches is recommended in some situations, it is not recommended to clear caches while the site is busy.  However you can run drush command (drush cc) to get a list of your caches elements. Then you can use the list to build something like that.

array=("menu" "css-js" "block" "module-list" "theme-list" "registry" 
"entitycache-comment" "entitycache-profile2" "entitycache-field-collection-item" 
"entitycache-node" "entitycache-file" "entitycache-taxonomy-term" 
"entitycache-taxonomy-vocabulary" "entitycache-user" "libraries" 
"metatag" "token" "views"); for i in "${array[@]}"; do drush cc $i; sleep 5; done