Performance optimisations

[gabrielnau]

Goal: keep overhead as low as possible over the Java lib.
TODO:

• advise on span/end positionnal vs options map
• However, both approaches introduce measurable overhead; in performance-sensitive contexts, we should only use
  positional parameters.
• https://clojure.org/reference/java_interop#optimization
• profile the code and try in https://github.com/bsless/stress-server project maybe, to have a good stress test
  ?
  • at least find a way to run a long time a stress test to validate there is no leaks -> it might be possible
    to test it even after a triggered GC event ?
• micro bench:
  • https://github.com/hugoduncan/criterium
  • https://github.com/jgpc42/jmh-clojure
• could be interesting to check https://github.com/jetty-project/jetty-load-generator
• would be interesting to have an example implementation e2e with dummy db backends and being able to load test
  it, to identity churn etc
• see https://github.com/bsless/stress-server
• might not be useful at all, but it can be interesting to
  use no.disassemble
• Load testing:
  • configure reitit properly (see stress server results)
  • use BatchSpanProcessor !
• reify type hints ?