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From Aaron Morton <>
Subject Re: Using a synchronized counter that keeps track of no of users on the application & using it to allot UserIds/ keys to the new users after sign up
Date Sun, 06 Feb 2011 21:02:10 GMT
If you mix mysql and Cassandra you risk creating a single point of failure around the mysql

If you have use data that changes infrequently, a row cache in cassandra will give you fast


On 5/02/2011, at 8:13 AM, Aklin_81 <> wrote:

> Thanks so much Ryan for the links; I'll definitely take them into
> consideration.
> Just another thought which came to my mind:-
> perhaps it may be beneficial to store(or duplicate) some of the data
> like the Login credentials & particularly userId to User's Name
> mapping, etc (which is very heavily read), in a fast MyISAM table.
> This could solve the problem of keys though auto-generated unique &
> sequential primary keys. I could use the same keys for Cassandra rows
> for that user. And also since Cassandra reads are relatively slow, it
> makes sense to store data like userId to Name mapping in MyISAM as
> this data would be required after almost all queries to the database.
> Regards
> -Asil
> On Fri, Feb 4, 2011 at 10:14 PM, Ryan King <> wrote:
>> On Thu, Feb 3, 2011 at 9:12 PM, Aklin_81 <> wrote:
>>> Thanks Matthew & Ryan,
>>> The main inspiration behind me trying to generate Ids in sequential
>>> manner is to reduce the size of the userId, since I am using it for
>>> heavy denormalization. UUIDs are 16 bytes long, but I can also have a
>>> unique Id in just 4 bytes, and since this is just a one time process
>>> when the user signs-up, it makes sense to try cutting down the space
>>> requirements, if it is feasible "without any downsides"(!?).
>>> I am also using userIds to attach to Id of the other data of the user
>>> on my application. If I could reduce the userId size that I can also
>>> reduce the size of other Ids, I could drastically cut down the space
>>> requirements.
>>> [Sorry for this question is not directly related to cassandra but I
>>> think Cassandra factors here because of its  tuneable consistency]
>> Don't generate these ids in cassandra. Use something like snowflake,
>> flickr's ticket servers [2] or zookeeper sequential nodes.
>> -ryan
>> 1.
>> 2.

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