"negative" caching means that there is a separate cache to cache failed user lookups for a while and return a failure immediately instead of re-trying the user lookup doing a (possibly expensive) user search in the underlying backend.It's a little bit like Squids negative_ttl, which is used to specify a duration for caching error responses. The negative cache allows the backend to "recover" and/or prevents backend overloading because otherwise every failing lookup would hit the backend again and again.
Oh right, well, again, should be fairly trivial to setup with python scripts and RAMCacheManagers.
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