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I'm really excited about RethinkDB, and am using it in my (yet-to-be-launched) startup. The new changes() support seems very interesting for my app, but for my use case I'd need several queries open per user (probably on the order of 10-100).

I missed the Q&A this afternoon, but I see lots of RethinkDB engineers on here... so, would there be severe performance implications of holding open that many cursors?



How many users are you expecting?

If you go over a couple 1,000 active changefeeds in 1.16, I recommend setting the `maxBatchSeconds` optional argument to `run` to something like 10 (the default is 0.5).

That change should significantly reduce the CPU overhead on the server if you have lots of idle changefeeds. Note that this does not affect how quickly changes get delivered - you will still get changes instantly.

The exact performance will of course depend on what queries you're going to run exactly, the rate of writes etc.


Thanks! I'll put together a test to see if I might run into any trouble.

(Related: the RethinkDB team is very responsive in the IRC channel. It's great to see how interactive they are with the community!)




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