Schema Design for High-Velocity Events | Dataford Interview Questions

Tell me about how you design a schema for high-velocity event tracking.

Using the provided event schema, write a query that summarizes activity during January 1 through January 3, 2026. Include event types with no matching events in that period.

Output

One row per event type with event_type_name, event_count, unique_users, and last_event_at.
Include zero-activity event types, with zero counts and a null timestamp.
Sort by event_count descending, then event_type_name ascending.

Schema

event_types

Column	Type	Description
event_type_idPK	INT	Stable identifier for an event type
event_type_name	VARCHAR(64)	Human-readable event type name

events

Column	Type	Description
event_idPK	BIGINT	Unique event identifier
event_type_id	INT	Referenced event type
occurred_at	TIMESTAMPTZ	Timestamp when the event occurred
user_id	UUID	Optional user associated with the event
source	VARCHAR(32)	Originating channel or system
payload	JSONB	Optional event attributes

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Problem