[anonymous-panda]

I think it’s far more mundane a reason. You can list 10k objects per request and getting the next 10k requires the result of the previous request, so it’s all serial. That means to list 1M files, you’re looking at 100 back to back requests. Assuming a ping time of 50ms, that’s easily 5s of just going back and forth, not including the cost of doing the listing itself on a flat iteration. The cost of a 10k item list is about the cost of a write which is kinda slow. Additionally, I suspect each listing is a strongly consistent snapshot which adds to the cost of the operation (it can be hard to provide an inconsistent view).

I don’t think btrees would help unless you’re doing directory traversals, but even then I suspect that’s not that beneficial as your bottleneck is going to be the network operations and exposed operations. Ultimately, file listing isn’t that critical a use case and typically most use cases are accomplished through things like object lifecycles where you tell S3 what you want done and it does it efficiently at the FS layer for you.

[tsimionescu]

That's 5s of a 15m duration. I don't think it matters in the least.

[anonymous-panda]

Depends how you’re iterating. If your iterating by hierarchy level, then you could easily see this being several orders of magnitude more requests.