PCA (Prometheus Certified Associate) sample exam question with answer 219

Question:
Which of the following queries contains a dimensional aggregation?

1. delta(node_mem_MemAvailable_bytes[1h])
2. avg_over_time(up[1d])
3. avg(up)
4. rate(http_requests_total{status_code=~`5\d\d`}[5m])

Answer:
C - In this query, avg is the dimensional aggregation. A dimensional aggregation: sum, min, max, etc. More at aggregation operators
A, D - this query does not contain a dimensional aggregation
B - over time aggregations are also known as temporal aggregations, not dimensional aggregations