We have a Customer Community with a custom Visualforce application that we built. After Winter '19 update on our production instance over the weekend, some of our query functions are timing out or running very slowly. These problems occur only for external users, not for internal Enterprise license users.
Our problem sounds similar to this post, however we have these differences:
One of our failed queries is on the User object. The query includes both external and internal users. The external users are all in the same account.
Another failed query is on the Case object. All cases are linked to accounts that are child accounts of the portal account in the hierarchy.
Our external users are using the old Customer Portal Manager Custom license, which is roughly equivalent of Custom Community Plus license.
I have a case open with Salesforce support, but I was wondering if anyone else had run into similar issues.