Is functions the best way to do this?

I am using appwrite as a backend service provider to build a booking system, and a frontend in nuxt.

Consider I have a calendar that allows users to book.

I obviously want to create a document level permission per user to achieve the restriction on the booking document.

However when checking availability they need access to all items in the booking table.

Is a function the only way to achieve this? I also wanted to maybe do some logic restrictions in the future on other creations so guess it applies here too.

Thanks