Authelia
The Single Sign-On Multi-Factor portal for web apps
... and React, authorization policies and many other backend tasks are completed in mere milliseconds and login portal loading times of 100 milliseconds makes it one of the fastest solutions available. Processors can use a lot of electricity, but when idle usage is basically so low that you can't measure it, and active usage in a small business environment being under 1% you can rest easy (with the exclusion of password hashing).