Auth0 costs ~$0.023 per active user per month at the volumes most Indian D2C startups operate at. For a brand at 100,000 MAU that's ~$2,300/month. For a 1M MAU app, it's ~$23,000/month. Which is fine if your gross margin per user is $5+. It's not fine if your average customer spends ₹300 a month on milk subscriptions.

This is the calculation that drives most of our Xenotix Labs backend decisions. Build the auth system, save the recurring fee. Buy the auth system, save 4 weeks of engineering. The right answer changes by company, and we've made both calls. Here's the framework we use.

What auth actually has to do for an Indian D2C app

Phone-OTP login (the default for India, not email/password)

Email/password as a fallback for older / NRI users

Social login (Google primarily; Apple for iOS users with iCloud accounts)

Magic link via WhatsApp or email

Session management with refresh tokens

Multi-device login + remote logout

Account recovery via the original phone OR email

Rate limiting on OTP requests…