[narism]

There are a number of circuit breakers in VictoriaMetrics that limit the number of time series/datapoints in queries to limit CPU/RAM usage. These can be tweaked with the -search.max* command line flags. I think the default query limits for data points per series are 30M and number of series is 300K.

What do you consider reasonable cardinalities or a true TSDB?

[hintymad]

In my particular example, the cardinality of the instances (i.e., the number of of unit instance count in a query's time range) should not even matter. I was summing a counter over all the instances, and VictoriaMetrics should just add up the counters for every time unit while scanning all the data points -- this is implemented by pretty much all the OLAP engines. Or put it another way, logically I was query over a single time series. It's just that each value in the time series was associated with multiple values. Given such logical model, a good time series database should not not even bother me with any concern of cardinality.