I should probably change the title of this topic 
What I’m looking for is the best way to improve the plugin’s performance that will work in both a normal WordPress installation and a multisite installation.
If using a webhook for keeping data synced between Discourse and WordPress is a good approach, the reason for wanting to have the embed_url returned with the post_event webhook, instead of storing that data on the WordPress end, is that the only way I can see of storing the data on WordPress is to create a new database table. That would be quite simple, but I’m trying to conform to the WordPress VIP coding standards. The hope is that the plugin can eventually be used on sites hosted by wordpress.com. The WordPress VIP coding standards do not allow creating or altering the WordPress database tables: https://vip.wordpress.com/documentation/vip/code-review-what-we-look-for/#database-alteration