SQL Baseline Spike Detection | Dataford Interview Questions

Write a SQL query to identify users whose request volume spikes sharply compared with their own historical baseline in Hiddenlayer’s data warehouse.

Use January through March 2025 as the historical baseline and April 2025 as the current month. A spike is a current-month request count at least twice the user’s average monthly baseline, with a positive baseline average.

Output

One row per qualifying user with user_id, email, current_month_requests, baseline_avg_requests, and spike_ratio.
Include only qualifying users, ordered by spike_ratio descending, then user_id ascending.

Schema

users

Column	Type	Description
user_idPK	INT	Unique identifier for a user
email	VARCHAR(255)	User email address

request_events

Column	Type	Description
request_idPK	INT	Unique identifier for a request event
user_id	INT	User associated with the request
requested_at	TIMESTAMP	Timestamp when the request occurred

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