  Many cloud service providers (CSPs) provide on-demand service at a price with
a small delay. We propose a QoS-differentiated model where multiple SLAs
deliver both on-demand service for latency-critical users and delayed services
for delay-tolerant users at lower prices. Two architectures are considered to
fulfill SLAs. The first is based on priority queues. The second simply
separates servers into multiple modules, each for one SLA. As an ecosystem, we
show that the proposed framework is dominant-strategy incentive compatible.
Although the first architecture appears more prevalent in the literature, we
prove the superiority of the second architecture, under which we further
leverage queueing theory to determine the optimal SLA delays and prices.
Finally, the viability of the proposed framework is validated through numerical
comparison with the on-demand service and it exhibits a revenue improvement in
excess of 200%. Our results can help CSPs design optimal delay-differentiated
services and choose appropriate serving architectures.
