This module allows the developer to define metatags for content pages, typically for the purpose of SEO or social sharing meta data.
When we last came across this module we were investigating performance issues. Specifically there was a page driven by the Views module with many nodes being output. In this particular scenario this module caused extra SQL queries to be sent to the database for each entity on the page. During entity_load() attachLoad() was called which fired off a query on the metatags table.
Ideally we would like to alter this behaviour so that data for all entities to be rendered on the page is fetched in one hit rather than as each entity is loaded.