Materialised Views

Yes, you can. You define your CDT just like you would for a regular view or table.

IS this possible in MY SQL (Appian Cloud)?

MySQL doesn't have materialized views. Nothing to do with Appian or Appian Cloud.

Whilst this is literally true, you could take a couple of different approaches to achieve the same sort of thing. If you think of a materialised view as a physical table that holds the results of the SQL that a VIEW would normally be constructed from, you could:

1. run a scheduler that periodically empties and then re-loads a table with the data that you want
2. add triggers to the relevant table(s) to manage the content of another table that would act like a materialised view

Both approaches have pros and cons.