"OTP"

OTP & SMS Verification System — Pepper Hashing + DB Rate Limiting + State Machine + Replay Attack Protection

In-depth analysis of the NestJS OTP verification system: SmsVerificationCode model with 17-field state machine design, SHA-256 Pepper hashing for leak prevention, 60s DB rate limiting + 5-attempt lockout, concurrent safe updates, Throttler dual protection, and production/development dual modes.