Summarize September API Endpoint Performance | Dataford Interview Questions

How do you optimize database performance for high-traffic applications?

For the SQL portion, write a query that summarizes active API endpoints using requests from September 2026. Include only endpoints with at least two requests during the period, while preserving efficient timestamp filtering.

Output

One row per qualifying active endpoint with endpoint_name, request_count, avg_latency_ms, and error_rate_pct.
Include requests with HTTP status codes of 500 or higher in the error rate.
Order by request count descending, then endpoint name ascending.

Output details

Treat September 2026 as the half-open interval from 2026-09-01 00:00:00 inclusive through 2026-10-01 00:00:00 exclusive.
Round avg_latency_ms to two decimal places.
Round error_rate_pct to two decimal places.

Schema

api_endpoints

Column	Type	Description
endpoint_idPK	INT	Unique API endpoint identifier
endpoint_name	VARCHAR(120)	Endpoint path or logical name
is_active	BOOLEAN	Whether the endpoint is currently active

api_requests

Column	Type	Description
request_idPK	INT	Unique request identifier
endpoint_id	INT	Referenced API endpoint
requested_at	TIMESTAMP	Time when the request was received
latency_ms	INT	Request latency in milliseconds
status_code	INT	HTTP response status code

Your question is Summarize September API Endpoint Performance. Start with the requirements and the two tables in the Question tab.

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