This has a large overhead - easily a few kilobytes per file, depending on filesystem. Poor locality - your data gets scattered across entire disk; even on SSD t

This has a large overhead - easily a few kilobytes per file, depending on filesystem. Poor locality - your data gets scattered across entire disk; even on SSD this matters to some extent. And also starts to break down in some ways already at O(100k) files, e.g. globs in command line stop working. You can work around by splitting files into different directories but at that point it's just easier to use a normal database.