You should not use waitUntil, Stripe will wait for your webhook response before redirecting, removing the need for a success page that checks that Stripe already sent the webhook

[remorses]

From Stripe docs https://docs.stripe.com/checkout/fulfillment?payment-ui=stripe-hosted#redirect-hosted-checkout:

When you have a webhook endpoint set up to listen for checkout.session.completed events and you set a success_url, Checkout waits for your server to respond to the webhook event delivery before redirecting your customer. If you use this approach, make sure your server responds to checkout.session.completed events as quickly as possible.

[odicho]

That's exactly what waitUntil is for! It allows you to queue the processing so it doesn't block you from proceeding, which allows us to return ASAP. The waitUntil allows the processing to finish asynchronously before shutting down the function.

https://vercel.com/changelog/waituntil-is-now-available-for-vercel-functions

[remorses]

If you use waituntil Stripe will redirect the user before you saved the subscription in your database

[odicho]

That's what syncStripeDataToKV is for. It will always call Stripe's API to check the subscriptions. Even if you get redirected to /success/ before the webhook is fully processed, we still check the subscriptions via the Stripe API.

I think the overall strategy is to use the webhooks as a trigger to go check the Stripe API. This way, we don't have to rely on the data that comes from the webhooks.

[santiagopuentep]

From Stripe docs https://docs.stripe.com/checkout/fulfillment?payment-ui=stripe-hosted#redirect-hosted-checkout:

When you have a webhook endpoint set up to listen for checkout.session.completed events and you set a success_url, Checkout waits for your server to respond to the webhook event delivery before redirecting your customer. If you use this approach, make sure your server responds to checkout.session.completed events as quickly as possible.

This is simply not truth. I just checked blocking all webhook responses (never responding to anything) and the checkout session redirects in the same way, so the Stripe docs seem to be wrong. I'm simply responding as soon as possible (since it has no effect) and saving the data in my db afterwards.

[remorses]

How much time did it take to redirect? Maybe there is a timeout

[santiagopuentep]

How much time did it take to redirect? Maybe there is a timeout

It redirects after it does whatever background job it has to do, no matter your response to any of the webhooks (you receive multiple webhooks while it's processing the checkout).