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== What algorithm does Nginx use to load balance?  Can it balance based on connection load? ==

Currently, Nginx has round-robin, least connections and ip-hash algorithms (all come with weights).

There are also a number of third-party modules for load balancing. 

Note: Many users have requested that Nginx implement a feature in the load balancer to limit the number of requests per backend (usually to one).  While support for this is planned, it's worth mentioning that demand for this feature is rooted in misbehaviour on the part of the application being proxied ''to'' (Ruby on Rails seems to be one example). This is not an Nginx issue. In an ideal world, this particular problem fix request would be directed toward the backend application and its ability handle simultaneous requests.