Which of the following metrics is unsuitable for a Prometheus setup?

The metric user_last_login_timestamp_seconds{email="john.doe@example.com"} isunsuitable for Prometheusbecause it includes ahigh-cardinality label(email). Each unique email address would generate a separate time series, potentially numbering in the millions, which severely impacts Prometheus performance and memory usage.

Prometheus is optimized for low- to medium-cardinality metrics that represent system-wide behavior rather than per-user data. High-cardinality metrics causedata explosion, complicating queries and overwhelming the storage engine.

By contrast, the other metrics—prometheus_engine_query_log_enabled, promhttp_metric_handler_requests_total{code="500"}, and http_response_total{handler="static/*filepath"}—adhere to Prometheus best practices. They represent operational or service-level metrics with limited, manageable label value sets.