Question

How fast can we download files from Amazon S3, is there an upper limit (and they distribute it between all the requests from the same user), or does it only depend on my internet connection download speed? I couldn’t find it in their SLA.

What other factors does it depend on? Do they throttle the data transfer rate at some level to prevent abuse?

Answer 1

This has been addressed in the recent Amazon S3 team post Amazon S3 Performance Tips & Tricks:

First: for smaller workloads (<50 total requests per second), none of
the below applies, no matter how many total objects one has! S3 has a
bunch of automated agents that work behind the scenes, smoothing out
load all over the system, to ensure the myriad diverse workloads all
share the resources of S3 fairly and snappily. Even workloads that
burst occasionally up over 100 requests per second really don’t need
to give us any hints about what’s coming…we are designed to just
grow and support these workloads forever. S3 is a true scale-out
design in action.

S3 scales to both short-term and long-term workloads far, far greater
than this. We have customers continuously performing thousands of
requests per second against S3, all day every day. […] We worked with other
customers through our Premium Developer Support offerings to help them
design a system that would scale basically indefinitely on S3. Today
we’re going to publish that guidance for everyone’s benefit.

[emphasis mine]

You may want to read the entire post to gain more insight into the S3 architecture and resulting challenges for really massive workloads (i.e., as stressed by the S3 team, it won’t apply at all for most use cases).