Ask HN: Phone Verification OTP Design Patterns

Hello HN,

Is there any standard design practice/pattern for mobile phone verification using One Time Pass-code (OTP) ?

Practical efforts to understand existing systems indicate that most of them use similar design. ( Oddly enough, I've not been able to find any such standards specifying the same)

Just to mention a few cases 1. Is there any standard specifying the exponential/sequential increase in time delay for handling resend requests ? 2. What is the recommended expiry time for a newly generated OTP ?

Do pull in any resources that you think might point to the same. Thanks!