InfluxDB is a time-series database that provides a way to query series cardinality, which refers to the number of unique values in each series. The series cardinality can be found using a specific SQL query. Additionally, Kapacitor TICKscript filters can be used to define multiple levels of filtering, but Kapacitor assumes that each level is a subset of the previous one, resulting in unexpected behavior if not designed correctly. To resolve this issue, filter criteria should be adjusted so that the WARN level includes values for the CRITICAL level. Furthermore, InfluxDB version 0.13 introduces a feature to log slow queries after a certain threshold, which can be configured using the `log-queries-after` setting in the configuration file.