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Why in the world would Stack Exchange rate limit searches?

I was just trying to do a search to find a dupe I knew was out there, and having a hard time between my typos and the arcane SE mechanism for ANDing search terms, got hit with this message:

You can only perform 6 searches within a 60 second window, please wait a moment and try again.

Could we please eliminate this rate-limit? Seems like it would simplify the code-base not to have it.

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Related: meta.stackexchange.com/questions/84311/… –  sarnold Jun 29 '11 at 22:32
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I have no problem with the rate limit, as long as it's way higher than 6 a minute –  Pëkka Jun 29 '11 at 22:34

3 Answers 3

Searches are very resource intensive; unbounded searches is a quick DDOS vector for the network.

If you can't live within the very generous 6 searches per 60 seconds allocation, I suggest using one of the many web search engines as a free, public alternative:

  • Google
  • Bing
  • DuckDuckGo
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@Jeff, just like with all the other denied search requests, the question is why can't we do it better? –  Lance Roberts Jun 29 '11 at 22:42
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@lance everything has to be rate limited; has nothing to do with 'better' but 'protecting the experience for everyone'. codinghorror.com/blog/2009/02/… aka why can't 7-11 make the experience better for students in the store? is the wrong question, my friend. –  Jeff Atwood Jun 29 '11 at 22:44
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@Jeff, good article, but we could still up the limit. DDOS will do A LOT more than 6/minute. –  Lance Roberts Jun 29 '11 at 22:48
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@Lance - 6/minute x millions of users on a botnet could potentially be an issue. Go get a sandwich or something. –  JNK Jun 29 '11 at 23:15
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It would not be possible to launch a DDOS attack if you leave the anonymous search limit as it is and add a much higher per-user rate limit for users with rep above some threshold. The attackers would need access to many hi-rep accounts to exceed what they can already do with no accounts. –  Rick Sladkey Jun 30 '11 at 1:17
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@Jeff but as @Rick points out, unlike the store owner, you have the means to identify trustworthy users. Why not relax the restriction a bit for users above 500 or 1000 rep? –  Pëkka Jun 30 '11 at 7:42
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If you can only handle 6 searches per user per minute, switch to something that scales better, like Rails. –  Andrew Grimm Jul 7 '11 at 1:24
    
@Andrew It has nothing to do with hardware or software performance... If you read the comments above you will see that the limitations are there as a preventative measure. –  chown Jul 10 '12 at 2:48

If all 20,000 active-ish users submitted six queries per minute or ten queries per minute, I imagine the site would be pretty well hammered with either setting.

Perhaps the scheduling algorithm could be more like an OS CPU scheduler: grant upwards of twelve to twenty queries per minute per user at idle and scale down to six per minute per user when under moderate load. (>60 searches in the last minute? >100 searches in the last minute?) You could scale even lower if you pass a boundary that suggests more than 100 accounts are involved in DDoSing via searches.

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up vote 3 down vote accepted

There is now no rate-limiting on searches with the new elasticsearch, as per here.

As per Pang's comment, looks like the limit is actually 30 searches in 60 seconds.

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Actually, it seems that the new limit is 30 searches per 60 seconds (I tested it on SO and meta SO). –  Pang Sep 3 '13 at 1:23

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