amazon S3 upload object LastModified date keep changed?

Question

We know that if we download a large file in linux or mac, the file last modified time will keep changed. Is that same in S3? The object last modified time will keep changed during uploading , or it just a simple timestamp to record the start of upload operation ?

Answer 1

Doc says After you upload the object, you cannot modify object metadata. The only way to modify object metadata is to make a copy of the object and set the metadata. ,i believe in order to maintain atomicity, if the put operation is successful then only it will update time.

Last-Modified,comes under category of system-defined metadata.

Last-Modified-> Description-> Object creation date or the last modified date, whichever is the latest.which a successful put operation will only update lastmodified time in other words.

modified date/time is updated by the S3 system itself, and reflects the time when the file completed uploading fully to S3 (S3 will not show incomplete transfers.) The last modified date of an object is a direct reflection of when the object was last put into S3.

even a similar answer says the same https://stackoverflow.com/a/40699793/13126651 - "The Last-Modified timestamp should match the Date value returned in the response headers from the successful PUT request."