Uber·Data Scientist·Technical Phone Screen
- For each user, write a SQL query to return the first product they purchased along with the purchase timestamp.
- Write a SQL query to count how many distinct users made at least two purchases on the same calendar day.
- Find the top 3 products by total number of purchases using SQL.
- Calculate a 7-day rolling average of total daily purchases across all users in SQL.
- Using pandas, compute daily active users from the same dataset, defined as the count of unique user IDs per date.
“Pretty standard first-purchase problem.”