IMO using Kafka for long term storage is not the greatest idea. It is expensive to keep CPU and RAM constantly on top of data that it going to be cold most of the time. There is no DML which means mistakes are expensive (from an engineering pov). And while the whole event sourcing paradigm can work quite well in narrow domains with teams fully aware of the implications of what they are doing, in practice, on large orgs, it is hard to scale (from a people perspective).