leventov commented on issue #4947: Historicals should only write to remote cache
URL: 
https://github.com/apache/incubator-druid/issues/4947#issuecomment-472180143
 
 
   > I think the local cache could help if the remote cache is churning too 
much. Since the local cache only stores results for segments located on that 
historical, it may keep results longer than a remote cache that stores results 
for all segments in the cluster. Of course it's possible to simply give more 
memory to the remote cache instead.
   
   Yes, you are right, the local cache is not needed (apart from the admission 
window) only if the remote cache is large enough.
   
   > But even in this situation, you can imagine a local cache being useful to 
keep results that haven't been deemed worth caching remotely yet. If another 
query for these results come in, then historicals could get results from the 
local cache instead of re-scanning the segments, and then potentially write 
these results to the remote cache if they are now considered worthy.
   
   It looks to me precisely like the description of the admission window.

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