User Interaction on Frontend:

Users choose a subscription plan and quantity on your React frontend (pricing.js).
Upon selecting a plan, your frontend sends a request to your backend endpoint to initiate the subscription process.
Backend Subscription Initialization:

The backend (/saas/subscribe endpoint) receives the request and creates a preliminary subscription record in your database with status new.
Using Stripe's SDK, it creates a Checkout Session with the relevant subscription details (price ID, quantity) and success/cancel URLs.
The backend sends the URL of the created Checkout Session back to the frontend.
Redirect to Stripe Checkout Session:

Your frontend redirects the user to the Stripe Checkout Session URL for payment processing.
User Completes Payment on Stripe:

The user completes the payment on Stripe's hosted checkout page.
Upon successful payment, Stripe redirects the user to the success URL specified earlier.
Webhook Notification:

Stripe sends a webhook notification to your backend (/stripe-webhook/) indicating the payment status and subscription details.
Your webhook handler updates the subscription status in your database to active upon successful payment or handles failures accordingly.
Post-payment Processing:

Depending on the webhook event type (customer.subscription.created, invoice.payment_succeeded, invoice.payment_failed), you update the subscription's status and other details in your database.
The frontend can show the updated subscription status to the user based on the success URL redirection or through a subsequent API call to fetch the subscription status.