PCA (Prometheus Certified Associate) sample exam question with answer 546

Question:
What is the difference between a counter and a gauge metric?

1. Counter metrics can only store whole number values while gauge metrics can store decimal values
2. Counter metrics are monotonically increasing while gauge metrics can go up or down arbitrarily
3. There is no such thing as a gauge metric
4. There is no such thing as a counter metric

Answer:
B - is the correct answer. More at metric_types
A - is incorrect as all Prometheus samples are float64 values and thus any type of metric can store decimal values, including counters
C - is incorrect as there is a metric type called gauge
D - is incorrect as there is a metric type called counter