When is it safe to use a broken hash function?

Question

It is trivial to use a secure hash function like SHA-256, and continuing to use MD5 for security is reckless behavior. However, there are some complexities to hash function

Answer 1

The answer entirely depends on what you're using it for. If you need to prevent somebody producing a collision with a few milliseconds I'd be less worried than if you need to prevent somebody producing a collision within a few decades.

What problem are you actually trying to solve?