In this video, I implement a production-ready multi-factor authentication (MFA) system in Spring Boot using Google Authenticator, JWT, and Redis. I start from my existing “JWT token stored in Redis” project (an industry-standard approach for token management), then I walk you through the architecture: login issues JWTs, Redis holds token state, and every protected request validates both the JWT and its presence in Redis. I also show the practical setup: PostgreSQL + Redis configuration, running the project, debugging a real startup issue (JDK mismatch), and testing login/logout behavior in Postman so you can see tokens getting stored and blacklisted in Redis. Then I build the MFA flow end-to-end: generating a per-user secret, building the otpauth URI, generating a QR code, and implementing the “setup” + “confirm” steps so MFA isn’t enabled until the user proves their authenticator app works. After confirmation, I force logout by clearing tokens from Redis, and I update the login flow so MFA-enabled users get a temporary token first, then exchange it with the OTP for the real access token. Along the way, I call out a key security mistake—storing the secret in plaintext—and I show how to address it with AES-256-GCM encryption (with proper IV handling and a master key loaded from config).