You can improve your website’s performance by using the WordPress Widget Cache feature to save widget output on transient for faster retrieval than with core widget display.
Should I use WordPress Widget Cache Output?
The answer is yes, especially when you are using widgets with third-party contents like Twitter tweets, Instagram feeds, and other services. These widgets always make calls, which takes load time. Other heavy resource widget outputs and WP_Query calls like Recent Posts, Recent Comments, Pages and other WP_Query-relient widgets also add load times which you can control using this caching option. You can set the time when you want them to be cleared or updated in order to save the fresh one.
If in any situation where you do not want several widgets to be cached, you can always go to the Widget Options settings tab and check “Do not cache this widget.” You have complete control over your widgets!