sentences:  Varnish is heavily threaded, with each client connection being handled by a separate worker thread.When the configured limit on the number of active worker threads is reached, incoming connections are placed in an overflow queue; when this queue reaches its configured limit incoming connections will be rejected.The principal configuration mechanism is "Varnish Configuration Language" (VCL), a domain-specific language (DSL) used to write hooks that are called at critical points in the handling of each request.