Rows belonging to accounts outside your scope are neither shown nor touched — they are copied through a save untouched. Two people saving in the same second no longer overwrite each other: the save is conditional on the version it read, and a clash is replayed against the newer file. If it clashes twice you are asked to reload rather than told it worked. AM at entry is stamped when a row is first published and never rewritten, so a credit keeps the name it was filed under even after the account changes hands; the change log records your alias against every value you save. Internal — do not share outside AWS.