By co-founder of Instagram

Many of my friends recently shared infographic about “How Instagram Started” or “How Two Guys Made an App in 8 Weeks”. They sure made an app in 8 weeks but UX tricks and technology behind the app are more complex than we think. “Speed Matters” in UX. Slides from 2011 by Instagram co-founder Mike Krieger



Law & Company


Tech for Korea Ads Pilot


The metrics used to analyze the profitability of subscription business



  • Monthly Average Revenue Per User (ARPU) ¬†= Subscription Revenue / Average Subscribers
  • Monthly Subscriber Churn Percent = Subscribers lost in month / Base of subscribers at beginning of month
  • Gross Margin Percent = Gross Profit (from subscribers) / Subscription Revenue
  • Subscriber Lifetime Value (LTV) = (Gross Margin Percent * Monthly Subscription ARPU) / Monthly Subscriber Churn Percent
  • Customer Acquisition Cost (CAC) = Sales & Marketing Expenses / Gross Customer Additions
  • Payback period (Breakeven points for each user) = Cumulative cash flow for average user
  • Subscriber Return on Investment (ROI) = LTV / Customer Acquisition Cost

Some metrics such as gross margin and customer acquisition cost are too generic, and can be applied to all types of businesses. Also, we should define / set the meaning of success, based on the past data of already successful subscription businesses.