* Threshold to evaluate if routee is considered to be busy (under pressure). Implementation depends on this value (default is 1).

• 0: number of routees currently processing a message.
• 1: number of routees currently processing a message has some messages in mailbox.
• > 1: number of routees with at least the configured `pressureThreshold` messages in their mailbox. Note that estimating mailbox size of default UnboundedMailbox is O(N) operation.

public int PressureThreshold { get; }

member PressureThreshold : int with get