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From Robert Coli <rc...@eventbrite.com>
Subject Re: Optimal Way to Tune For Searchs For Missing Keys
Date Thu, 09 Jan 2014 23:11:16 GMT
On Thu, Jan 9, 2014 at 1:42 PM, Charlie Mason <charlie.mas@gmail.com> wrote:

> There are a lot more reads than writes on this particular table. All of
> the queries are just for the partition key. Most of the queries are for
> partition keys that don't exists, more than 99% of the queries.
>

Reads for partition keys that don't exist are the fastest reads Cassandra
can do, because it can usually correctly answer the "exists?" question from
bloom filters, which are resident in RAM. If the bloom filter says the row
does not exist, the key cache is not even consulted. You have an extremely
low number of bloom filter false positives relative to number of reads, so
it is likely that you cannot further optimize requests to this column
family.

(Why is your application asking for so many keys which don't exist?)

=Rob

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