Mongodb does persistent storage database, is it necessary to use redis to do another layer of cache?

  mongodb, question

Mongodb does persistent storage database, is it necessary to use redis to do another layer of cache?

Ps: I observed the mongodb server process myself. Even if the amount of data is very small (with a capacity of more than 1g), it takes up more than 1g of memory when running. Does mongodb realize a set of cache for storing hot data?

Redis does caching only to speed up application or website access and reduce database pressure, which is the purpose of caching.
If mongodb’s access speed is normal and the pressure is low, then cache is not needed.