Is the conversion event counted for users who have not logged a visit?
When the visit and conversion event are separated in time, like sign up -> purchase, it's possible for some users to have visited before the experiment begins, but hit the conversion event while the experiment is running. Will Amazon A/B testing remember visits on a per-user basis so that it can avoid counting conversion events for users whose visits weren't measured, or is it the responsibility of the app to do that?
If the conversion events are greater than the number of views in an A/B Test, then there is something wrong with the events that are chosen to be the views and conversion events and the A/B test results will be meaningless. A/B testing does not track on a per user basis, your app would need to track that too if you want to track per user. If you want to track per user for a period of time, you would have to add the logic to your app that makes sure that a view and potential conversion event is only recorded once per user for the period of time (a cool-off period). This will allow for users who make multiple view-conversions in a given time period not to influence your overall result because they would only be counted once in that time window.