I have seen saas products having pay as you go structure. How should one handle such payment structure? Lets say I have social media app and user creates post. Now first 100 posts are free but after that every 100 posts application should charge $1. Any general approach to solve such problems? any suggestions/recommendations how can this be done?

You just calculate it at the end of the month and charge them the amount (assuming you've their credit card on file). Nothing special.

Got it

Note: Due to the recent RBI restrictions regarding recurring payments, you might need to send some sort of notification for approval for Indian customers. See: https://www.business-standard.com/article/pf/new-auto-debit-rules-of-rbi-to-kick-in-from-friday-what-you-need-to-know-121093000707_1.html

Ok let me check this

Are you talking about bank mandates or simple bank transfers? Because normal bank transfers aren't automated.