Improving JsonSerializer performance (System.Text.Json)

A .NET 6 project that I’ve been contributing to uses the new(ish) System.Text.Json JsonSerializer to serialise/deserialise data prior to storing to, and after retrieving from, a distributed cache.

I started to notice some performance degradation as I increased our use of caching in this application (and therefore more JSON serialising/deserialising going on), so set to work on investigating why this was the case.