A set of three-tier e-commerce cluster architectures are analyzed: rigid, in which no machines are shared between tasks; flexible, in which all machines are shared; and hybrid, in which some machines are shared. Each architecture?s performance space is mapped and trade-offs are discussed. Steady-state and temporary transient overload conditions are simulated. Simulation indicates that the hybrid architecture?s steady-state performance is better than the rigid architecture and within three percent of the flexible architecture in the likely operating region. While the flexible architecture always drops order messages during transient overload, the hybrid architecture only begins dropping orders when they compose more than six percent of the messages. In addition, when order messages are dropped, the hybrid architecture drops fewer than the flexible architecture.