WCF there are three types of Instance Management
• You want a stateless services
• your service hold intensive resources like connection object and huge memory
• Scalability is a prime requirement. You would like to have scale out
• Your WCF functions are called in a single threaded model.
• You want to maintain states between WCF calls.
• You want ok with a Scale up architecture.
• Light resource references
• You want share global data through your WCF service.
• Scalability is not a concern.