Make sure the products or subscriptions you want to offer are set up correctly in the payment provider. Also make sure to use the production mode of your payment provider as Stripe and Polar both offer test modes, that you should not use in production.
Things to check:
All products and subscriptions are set up correctly in production mode
If you have set up billing for your app, you need to set up webhooks for the payment provider to sync the purchases to your database.
If you have done this already, make sure you are using the production keys and environment variables. Also make sure that the webhook is pointing to your production url.
Things to check:
You are using the production keys and environment variables from your payment provider
Especially for the marketing pages you want to make sure that the SEO is set up correctly, so that the pages can be found and indexed by the search engines.
When your have deployed your app to a cloud provider that runs your app (or at least the serverless functions) in a specific region (like Vercel does), you need to make sure that you have selected a region that is:
Close to your database location
Close to your target audience
This is important as the latency between the user, the server and the database can have a big impact on the performance of your app.
When you target a global audience, prioritize the first point or choose a platform that has multiple regions. If you deploy to multiple regions, you want to have a globally distributed database too, as otherwise the latency can be too high from some regions.
Things to check:
App is deployed to a region close to your database location
App is deployed to a region close to your target audience