FolioVision

There’s one problem with Gravatars. They are very slow to load. Each page with comments on them makes one call per comment to the Gravatar server. While a single call takes only a 100ms, on a page with hundreds of comments, we are talking about major slowdowns. Page loads can take 20 seconds and more.
This plugin solves this problem by:
<ul>
<li>
caching gravatars with WordPress cron job..
</li>
<li>
caching gravatars on comment submission
</li>
<li>
maintaining a single copy of the default gravatar instead of downloading it again and again for all the email addresses with no gravatar associtated
</li>
</ul>
<a href="http://foliovision.com/seo-tools/wordpress/plugins/fv-gravatar-cache/installation" rel="nofollow ugc">Installation guide</a>
<a href="http://foliovision.com/seo-tools/wordpress/plugins/fv-gravatar-cache" rel="nofollow ugc">Support and more information</a>

FV Gravatar Cache

I deactivated plugin but still contains elements in Database

Database Junk

Speeds up your website by making sure the gravatars are stored on your website and not loading from the gravatar server.

文派翻译（WP Chinese Translation）

<h3>Replace Gravatar with Cravatar, a perfect replacement of Gravatar in China.</h3>
More information at <a href="https://wpavatar.com" rel="nofollow ugc">https://wpavatar.com</a>
Privacy Terms <a href="https://wpavatar.com/privacy" rel="nofollow ugc">https://wpavatar.com/privacy</a>
How to use the WP Avatar:
For the first time use, you only need to activate this plugin without any action.

WPAvatar

Use WPAvatar to speed up your website, switch gravatar to Chinese source, and support automatic acquisition and display of QQ Mail avatar.

FV Gravatar Cache vs WPAvatar