So this is a great point that I forgot about. Yes, it's a problem for sure, but definitely not unaddressable. The databases community has been thinking about ha

So this is a great point that I forgot about. Yes, it's a problem for sure, but definitely not unaddressable. The databases community has been thinking about hashing schemes that address this issue since the 80s, like linear hashing, extendible hashing and consistent hashing. The trick is often around amortizing the cost of rehashing over insertions (no background tasks needed!), or somehow minimizing the amount of remapping and rehashing that needs to be done by using clever positioning. So yeah, like anything, it's a tradeoff and not a cure-all, but it can be done quite well.