An actual directory knows its direct children. An actual directory A with 2 child directories A/B and A/C, each of which with 1 million files, doesn't need to

An actual directory knows its direct children. An actual directory A with 2 child directories A/B and A/C, each of which with 1 million files, doesn't need to go through millions of entries in an index to figure out the names of B and C. It's also not possible for A and A/ to exist independently, and for A to be a PDF, A/ an MP4 and A/B a JPG under the A/ ”directory". All of which are possible, simultaneously, with S3.