Varnish settings To see further description of these settings, also check param.show -l in the Varnish management interface. -p thread_pool_max=4000 (default 1000) This number should be as low as possible, but with an upwards margin. Do not set it much higher than you need, that only leads to thread pile-ups. The "correct" number is something like the 90% centile number of concurrent requests when