While a multipart upload is still active, you can keep adding parts as long as the total number is less than 10,000. When you split the object into individual parts, each part can be as large as 50 GiB. The explanation is that a multipart upload allows you to upload a large object in parts, which can improve performance and reliability. You need to split the object into parts yourself and upload each part separately using the Multipart Upload API. You can add parts to an active multipart upload until you reach the maximum number of 10,000 parts per upload. Each part can range from 10 MiB to 50 GiB in size, except for the last part, which can be any size.