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Most consumer cell phone images are maybe 5 MBytes, so we're talking about 1/20th of 1 second. If you have a 1 Gbit/sec network in your home (which is really getting quite common), you can download or upload a 100 MByte image in about 1 second. The qualifier "slow" depends on the sizes of files you are downloading and uploading, the network connection you have, and what you mean by "slow". Uploading and downloading the same file over and over again will be.
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I feel like there are some assumptions built into that I just want to make really explicit, so breaking down a few of the phrases: In general, cloud storage is meant for long-term storage and/or serving files to other computers on the Internet - uploading and downloading the same file over and over again will be expensive and slow. Disclaimer: I work at Backblaze so I'm biased, you should keep me honest.
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