For example, Facebook’s goal for new users is to get them “7 friends in the first 10 days”. Twitter on the other hand has discovered that people who followed 30 people they basically became an active user forever.
Retention is what happens when, after convincing a user to sign up for your product, you lead them along a path of steps that creates such a positive user experience, it cements the value of your product in their mind.
Finally, there are engineering challenges to personalize artwork at scale. One challenge is that our member experience is very visual and thus contains a lot of imagery. So using personalized selection for each asset means handling a peak of over 20 million requests per second with low latency. Such a system must be robust: failing to properly render the artwork in our UI brings a significantly degrades the experience. Our personalization algorithm also needs to respond quickly when a title launches, which means rapidly learning to personalize in a cold-start situation. Then, after launch, the algorithm must continuously adapt as the effectiveness of artwork may change over time as both the title evolves through its life cycle and member tastes evolve.