Amazon S3 is eventually consistent, which means that an operation which overwrites existing objects may not be immediately visible to all clients and queries. As a result, later operations which query the same object's status or contents may get the previous object; this can sometimes surface within the same client, while reading a single object.

Avoid having a sequence of commands which overwrite objects and then immediately working on the updated data; there is a risk that the previous data will be used instead.