Redis is primarily an in-memory data store. This means that at one point in time, certain keys may get evicted. The design decision is simple - if you want all your data to be persisted forever, Redis would definitely be a wrong choice here. However, if this is temporary and you can handle a few faults, then you can go with Redis.
Even though it is not possible to directly simulate the WHERE clause behaviour, it is possible to do it.
For this, you can use the ZRANGEBYSCORE command in Redis.
So, what you can do is as and when the words come, use the ZSCOREcommand to get the current score and update it to whatever you want using the ZADD command.
When you are querying, use the ZRANGEBYSCORE command to get the entire list and then choose the entry based on your need.