We would like to create a separated Autocomplete dictionary for each user, to store their search terms history. Assuming we have roundly 2 million users and each of them should have 5 history terms, is it possible and recommend storing as many dictionaries in a redis server?
The only limitation is the amount of memory you have, as long as you have enough memory to create 2 millions keys (each dictionary is a key in redis) with 5 terms each, there should be no issue with it.