mkdir -p -m 755 /usr/local/foo is safe, is it not?

• mkdir -p -m 755 /usr/local/foo is safe, is it not?
• It started taking down part of google production before someone pushed the emergency switch and stopped the rollout
• TL;DR: /usr/local/foo is created with 755 but then the user umask is applied (often 0027 or 0077 for safety).
• During testing, the tester had permissions to traverse /usr/local
• At install time, /usr/local/ got created with permissions 700 and broke everything as non root processes got access denied.
• Ultimately it’s all about relative speed of rollout, watching and being able to stop and revert quickly.

Chmod-Gate