Friend or Foe?
In mathematics, cardinality is the measure of the number of elements (distinct values) of a set. For example, the set {200,404,503} contains 3 elements so the cardinality of it is 3. But what does “High Cardinality” have to do with (time series) metrics?
Glad you asked, the answer is everything. :)
The rabbit hole goes infinitely deep if you want to do latency measurements, benchmarking, and performance testing/tuning/analysis. They are very hard to do right and it is very easy to mess them up. In this post, I would like to show you a very common mistake (that is just 0.000001‰ of the tip of the iceberg) and an extremely simple solution to fix it.
