Identify Unique Callers and French Customer Call Percentage

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Q: What difficulty level is this coding question?

This is a Medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Technical Screen rounds at Meta.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates at Meta during technical interviews.

Question

video_calls

+---------+-----------+--------------+---------------------+---------------+
| call_id | caller_id | recipient_id | start_ts            | caller_country|
+---------+-----------+--------------+---------------------+---------------+
| 1       | 101       | 202          | 2023-05-01 10:00:00 | US            |
| 2       | 101       | 303          | 2023-05-02 11:15:10 | US            |
| 3       | 202       | 101          | 2023-05-02 12:00:00 | FR            |
| 4       | 202       | 404          | 2023-05-03 09:55:00 | FR            |
| 5       | 303       | 101          | 2023-05-04 14:00:00 | GB            |
+---------+-----------+--------------+---------------------+---------------+

##### Scenario

Querying the video_calls table to answer recent usage questions.

##### Question

How many unique callers have called more than three distinct people in the last seven days? What percentage of customers from France made at least one video call yesterday?

##### Hints

Use COUNT DISTINCT, GROUP BY caller_id, HAVING clauses, date filters, and ratio calculations with CASE.

PracHub · Accepted Answer

This question evaluates proficiency in data manipulation, specifically aggregation and deduplication of user activity, time-based filtering of recent events, and computation of proportions using SQL or Python.

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