Меня пугают такие упоминания
Cached tracing produces a single linear trace of the actions an IO program takes. This tracing mode uses heuristics to determine call-site information on functions like flatMap and async, and those heuristics can be misleading, particularly when
used with monad transformers or types like Resource or Stream. If you have ideas for how to improve these heuristics, please let us know!
Full tracing captures a full JVM stack-trace for every call into IO, which results in an extremely comprehensive picture of your asynchronous control flow. This imposes a significant performance cost, but it makes it possible to see through complex compositions such as monad transformers or third-party code. This is an appropriate mode for development when the heuristics which generate a Cached trace are insufficient or misleading.
Я однажды пытался понять по трейсу, откуда дубевый запрос упал. Так и не нашел, там фигня какая-то была. В итоге нашел иначе. И понял, что трейс котовий не туда указывал. Видимо, эвристика подвела. С тех пор больше не пробовал трейсы.