You are a PM at Meta Pay. How are you going to measure success?

Metric questions are answered under this broad umbrella

Most of these metric should be broken down by various segment - apps (FB, Insta, WA), Causes (Donation, In app payment, peer to peer etc.)

Acquisition

• Number of users who signed up
• Number of users who entered their card details but never paid
• Number of users who used it to complete the payment - Break this down 

Activation/ Engagement

• Number of active users
• Number of payments per user 
• Frequency of payment - in various time frames like a week, month etc

Monitization

• Revenue per transaction
• Revenue per user
• GMV 
• Average transaction value

Retention 

• Number of users who stopped using the app after a certain time
• CLTV - Customer Lifetime Value

Some other important metrics could be

• Fraud transactions
• Failed transactions