I will be the first one to admit that I don't know participate in the date aggregation point of the pipeline so my knowledge is rusty. Say one was designing a s

I will be the first one to admit that I don't know participate in the date aggregation point of the pipeline so my knowledge is rusty. Say one was designing a system where age, sex information was important. How do you keep track of this information: 1. Across multiple computers that the person might be using? 2. Expiring cookies? Thanks