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:
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caching gravatars with WordPress cron job..
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caching gravatars on comment submission
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maintaining a single copy of the default gravatar instead of downloading it again and again for all the email addresses with no gravatar associtated
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<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.

FV Gravatar Cache vs One User Avatar | User Profile Picture