Optimizing Slow SQL Queries | Dataford Interview Questions

Describe a time you had to optimize a slow SQL query or a data-heavy backend process.

Using the supplied schema, write a PostgreSQL query that returns recent activity totals for active accounts. The result must include active accounts with no matching activity and should restrict activity to the first quarter of 2025.

Output

One row per active account, with account_id, account_name, and event_count.
Include accounts with zero matching events.
Order by event_count descending, then account_id ascending.

Schema

accounts

Column	Type	Description
account_idPK	INT	Unique account identifier
account_name	VARCHAR(100)	Display name of the account
status	VARCHAR(20)	Account status

activity_events

Column	Type	Description
event_idPK	INT	Unique activity event identifier
account_id	INT	Account associated with the event
event_type	VARCHAR(30)	Type of activity recorded
occurred_at	TIMESTAMP	Timestamp when the event occurred

Your question is Optimizing Slow SQL Queries. Start with the requirements and the two tables in the Question tab.

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Problem