Cache table filling too quickly
I'm not sure if it's the same thing, but if the queries you are caching are complex (nested queries, etc), it may be caused by the queries being serialized in Craft 3. Have a look at Brad's answer to a question I had a while go, to see if it covers your case as well:
Caching in Craft 3 causes out of memory when including grouped for loop

I ended up using the Cache Flag plugin to work around this.