CACHING IS UNCERTAIN. •There’s no cache-control header so it’s left to the client to decide. •iOS most likely will cache between 6 hours and 1 day and will always revalidate. •Android it depends, but most likely won’t cache.
DON’T LET THE CLIENT DECIDE. •Add the x-amz-meta-Cache-Control header when doing a PUT to S3. •It’s recommended to use a max-age of at least one month. •Don’t use x-amz-meta-Expires. The object will not be cached after its expiry date.