best varnish architecture for high concurrency site

John Cihocki john at
Thu Feb 20 14:59:06 CET 2014

How many concurrent client connections do those 6000 concurrent users
generate? You'll need to make sure you have enough available worker threads
to accommodate those users plus extra to soak up traffic spikes, ideally.

a) One thing to consider with a single instance architecture is the lack of
redundancy. If that host goes down, your site is down.
b) Do you mean have persistent client connections to backend, like
websockets? Or have varnish make backend requests through persistent
connections. The former is possible, the latter is the default behavior as
I understand it -- Varnish will always attempt to reuse an existing
connection for the next backend request.
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