Approach or strategy for storing object collections in Cache - caching

Question

I am trying to store collections of objects in cache.
{
"name": "Dep1",
"employees": [{
"id": 1,
"name": "emp1",
"profilePic": "http://test.com/img1.png"
}, {
"id": 2,
"name": "emp2",
"profilePic": "http://test.com/img2.png"
}, {
"id": 3,
"name": "emp3",
"profilePic": "http://test.com/img3.png"
}, {
"id": 4,
"name": "emp4",
"profilePic": "http://test.com/img4.png"
}]
}
In this case if Employee 1 changes his profile picture, I need to invalidate the full cached object in order to maintain data consistency.
This approach undermines caching as whenever there is any update for an employee I need to clear that complete object.
Is there any better approach or design we can be followed to optimize this?
Thanks

Answer 1

Is this suppose to be a redis question? I'll assume it's general purpose.
Retrieve only IDs then request each entry by it's ID.
Store the list of entries per request as merely the list of IDs.
You can now cache the list, as well as cache each entry.
Since you are only retrieving IDs you can make very simple super efficient indexes on the data (the data will always be fetched directly from the index since it's just the ID). Updates may or may not need to invalidate the cache of the list, it may be sufficient to invalidate the entry cache. Even if you invalidate the list you will still have fairly good performance since you're very unlikely to invalidate entry caches all too often.