Trace vs Log Per Event: A Decision Tree

Some events belong in logs; some in traces. The decision tree that picks the right place per event class.

Trace if

It is part of a request flow. Spans are units of work within a trace.

It needs context propagation. Traces carry context naturally.

Log if

It is async or batch. Logs are independent of request context.

It contains high-cardinality info. Traces have attribute budgets; logs do not.

Both if

High-stakes events deserve both. Trace for in-flow context; log for searchability.

Cost of both is small for important events; the redundancy is worth it.