for scalability in real world environments, not in labs / simulations ◦ App Engine is a proprietary technology ◦ Impossible to derive any model from the implementation ◦ We don’t have any information for the global state of the cloud environment • Benchmarks are a valid tool for case studies ◦ App Engine has no advanced monitoring for customers ◦ Only reliable way is to measure response times • Goal: form a strong chain of evidence 12