You might also need different systems for low-cardinality, low-latency production monitoring (where you want to throw alerts quickly and high cardinality fields would just get in the way), and medium to long term logging with wide events.

Also if you're going to log wide events, for the sake of the person querying them after you, please don't let your schema be an ad hoc JSON dict of dicts, put some thought into the schema structure (and better have a logging system that enforces the schema).