Not a real answer to your question, but for the last number of years I've been using Command-t (https://github.com/wincent/command-t) and after the initial index operation, it's super quick.
It's interesting that ido-mode doesn't first create a cache, and the built-in functionality available via elisp seems to be sufficient for speedy performance.
It's interesting that ido-mode doesn't first create a cache, and the built-in functionality available via elisp seems to be sufficient for speedy performance.