This should work in both ways.
The client knows what is the node version.
The node knows what is the client version.
So basically, if one knows he should not send a new data because the other one is too old, it will simply ignore it.
Same for reading. If your node is newer, he knows that the client won’t provide X or Y value. So he won’t try to read it.
That said, the best thing to do is to test it! 
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David Pilato - Developer | Evangelist
elastic.co
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Le 21 avr. 2015 à 15:39, Costya Regev costya@totango.com a écrit :
Another Question : if i will upgrade my Elasticsearch Client to Version 1.5.1 and my Elasticsearch Servers will stay on version 1.4.2 will it work ? it there a backward compatibility ?
On Tuesday, April 21, 2015 at 4:21:38 PM UTC+3, Costya Regev wrote:
Just checking ,
so you are sure that there is forward compatibility... and my system will work fine with Es Client version of 1.4.1 when the server's version will be 1.5.1 , right ?
On Tuesday, April 21, 2015 at 3:12:44 PM UTC+3, David Pilato wrote:
It should work fine.
--
David 
Twitter : @dadoonet / @elasticsearchfr / @scrutmydocs
Le 21 avr. 2015 à 14:08, Costya Regev <cos...@totango.com <>> a écrit :
Hi ,
We have Elasticsearch Servers running with Es Version 1.4.2,our client version is 1.4.1.
We are about to upgrade our Es cluster Version to 1.5.1 , my question is :
Do we need to upgrade the client version to 1.5.1 or our current version should be compatible with the new Version?
Thanks,
Costya.
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