How to Save User Data After Google Login (Next.js + Express + MongoDB)

[constant-infinite]

Hi everyone,

I'm currently developing a full-stack application using Next.js (TypeScript) for the frontend and Express for the backend. I've implemented Google OAuth login, but I'm unsure about the best timing and method to store user data into MongoDB.

Here's the general flow I'm considering:

1. Google login is triggered on the frontend → token is received
2. Token is sent to the backend
3. Backend verifies the token and extracts user info
4. User info is saved to MongoDB (or looked up if already exists)

Does this approach seem correct? Or are there better patterns for this?

I'd appreciate any advice especially on the following:

• Handling new vs existing users
• JWT vs session cookies
• API design best practices (keeping front/backend concerns separated)

Thanks in advance for your insights! 🙏

[hiroshi960617]

Hey @constant-infinite! 👋 Your flow looks solid and is a common pattern for Google OAuth in full-stack apps. Here’s a quick breakdown and some tips:
✅ Yes, your flow is correct:
Frontend triggers Google login → gets id_token
Send id_token to backend (POST /auth/google)
Backend verifies token (using google-auth-library)
Extracts user info → checks MongoDB
Creates user if new, or returns existing user

[hiroshi960617]

thank u

[caribbean961]

🔐 JWT vs. Session Cookies:
JWTs (in HTTP-only cookies): Great for API-first + Next.js
Sessions: Easier to manage but needs server-side session store
👉 Use JWT + refresh tokens for modern, stateless flow
📦 API Design Tips:
Keep auth logic in /api/auth/google
Use Express middleware to protect routes
Frontend just handles UI/token → backend handles logic + DB