Streak Calendars & Tracking Data Question(s)

Hello! Have any of you implemented a streak calendar for your app or software? This seems like such a compelling and engaging feature to implement and keep users attention daily / weekly. If so, did you come up with an efficient way of storing the data? I'm wondering if it's better to log it row by row for each day of a streak per user or to have one row per user with multiple columns (and, possibly arrays within those columns). By my comments, you can probably tell we're storing our data in tables. How did you do it on your end?