is there something about garbage collection a rails application needs to
worry about? if models(i.e model.new) are being created eveytime a user
visits a page, does that memory get ‘held up’ some place? does it need
to be freed?
No, Ruby does garbage collection for you.
if there are multiple requests/updates to a table from multiple users,
does rails handle mutex/data protection? or is this not an issue?
Active Record supports both optimistic and pessimistic locking.
Add a lock_version integer not nil default 0 column to your table to automatically enable optimistic locking.