How come you know those specifics are crucial ones?
Keeping in mind KPIs may differ from business to business and products to products, few of the major KPIs could be;
➤No. of signups (shows users are interested to try your product)
➤No. of logins by registered users ( may gauge users continued interest)
➤No. of forgetting password requests (evaluate if social signups or logins need to be activated)
➤No. of sessions by logged in users (( may gauge users continued interest)
➤No. of users exposed to paywall
➤No. of users taken action against paywall
➤No. of users continued payment processing
➤No. of users abandoned payment processing
➤No. of times payment processing failed
➤No. of users edited payment methods after the first payment
➤No. of users renewed subscriptions or services
➤No. of users raised a support ticket
What more KPIs would you like to add that help in better decision making?
Yes, and built a service for tracking them: https://everview.app
Although, am finding that KPIs are not a primary focus for a lot of founders (which is surprising).