It should not be. After caching, it must not hit database, until cache expires.
So, after the cache is set and you insert something, then it'll take time until cache expires, to have another db hit. Unless db is queried again, new data will not be there. It's as simple as that. As others said, you probably don't need caching, but if you do, set an expire time considering how fast the data in db get changed.
