Abstract author into private method

app/finders/autocomplete/users_finder.rb

@@ -2,6 +2,8 @@
 
 module Autocomplete
   class UsersFinder
+    include Gitlab::Utils::StrongMemoize
+
     # The number of users to display in the results is hardcoded to 20, and
     # pagination is not supported. This ensures that performance remains
     # consistent and removes the need for implementing keyset pagination to
@@ -31,7 +33,7 @@ module Autocomplete
         # Include current user if available to filter by "Me"
         items.unshift(current_user) if prepend_current_user?
 
-        if (prepend_author? && author = User.find_by_id(author_id)) && author.active?
+        if prepend_author? && author&.active?
           items.unshift(author)
         end
       end
@@ -41,6 +43,12 @@ module Autocomplete
 
     private
 
+    def author
+      strong_memoize(:author) do
+        User.find_by_id(author_id)
+      end
+    end
+
     # Returns the users based on the input parameters, as an Array.
     #
     # This method is separate so it is easier to extend in EE.