PCA (Prometheus Certified Associate) sample exam question with answer 311

Question:
What is the purpose of a counter in Prometheus?

1. To represent a single numerical value that can arbitrarily go up and down
2. To sample observations and count them in configurable buckets
3. To represent a single monotonically increasing counter whose value can only increase or be reset to zero on restart
4. To calculate configurable quantiles over a sliding time window

Answer:
C - correct answer. Counter represent a cumulative value, that can only increase over time or be reset to zero on restart