Slow nodes will be canceled due “to long tail cut”, so you would upload to the fastest nodes and download from the fastest nodes (110 nodes will be selected for upload and uploads will be cancelled when the first 80 are finished, and 39 nodes will be selected for download and downloads will be cancelled when the first 29 are finished - you need to have only 29 pieces from 80 to reconstruct a segment).
The Storj network has achieved strong read-after-write consistency. Your object will not be available until you have finished uploading.