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What difficulty level is this interview question?

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

What role is this question designed for?

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

Find the most-used app | Meta Interview Question

Q: Find the most-used app

This question evaluates data manipulation and metrics-definition skills, emphasizing SQL and Python proficiency for aggregating user activity and joining app metadata within analytics workflows.

You work on Oculus app engagement analytics.

Tables

`user_activity`

user_id (BIGINT)
date (DATE) — day of activity (assume UTC unless otherwise specified)
app_id (INT)
session_id (VARCHAR)
duration (INT) — session duration in seconds

`apps`

app_id (INT, PK)
app_name (VARCHAR)
app_category (VARCHAR)

Relationship: user_activity.app_id → apps.app_id.

Task

For the last 7 days (inclusive) relative to a provided :as_of_date, identify the “most used app.”

Write a SQL query that returns the most-used app using one clear definition of “most used” (e.g., number of sessions or total time spent ).
In 2–3 sentences, explain the pros/cons of at least two plausible definitions (e.g., sessions vs. total time vs. unique users).

Output

Return exactly one row with at least:

app_id
app_name
your chosen usage metric (e.g., session_cnt or total_duration_seconds )

Assume ties do not need a deterministic tie-breaker unless you choose to add one.

Tables

user_activity

user_id (BIGINT)

date (DATE) — day of activity (assume UTC unless otherwise specified)

app_id (INT)

session_id (VARCHAR)

duration (INT) — session duration in seconds

apps

app_id (INT, PK)

app_name (VARCHAR)

app_category (VARCHAR)

Relationship: user_activity.app_id → apps.app_id.

Task

For the last 7 days (inclusive) relative to a provided :as_of_date, identify the “most used app.”

Write a SQL query that returns the most-used app using one clear definition of “most used” (e.g., number of sessions or total time spent ).

In 2–3 sentences, explain the pros/cons of at least two plausible definitions (e.g., sessions vs. total time vs. unique users).

Output

Return exactly one row with at least:

app_id

app_name

your chosen usage metric (e.g., session_cnt or total_duration_seconds )

Assume ties do not need a deterministic tie-breaker unless you choose to add one.

Find the most-used app

Quick Overview

Tables

`user_activity`

`apps`

Task

Output

Submit Your Answer

Find the most-used app

Quick Overview

Tables

`user_activity`

`apps`

Task

Output

Submit Your Answer