I'd highly discourage you from using SMS; it's very insecure. I'd go as far as to recommend you not to implement your own auth and instead use something like Auth0, WorkOS, SuperToken, or SSOReady (https://github.com/ssoready/ssoready), among others.
Building auth stacks is not trivial and is not what will make your SaaS successful. The more you can leverage experts to focus on what makes your SaaS special, the better.
Building auth stacks is not trivial and is not what will make your SaaS successful. The more you can leverage experts to focus on what makes your SaaS special, the better.