Todd Hoff's High Scalability Blog is a destination  for developers tasked with building Web apps that scale. One of the blog's best features is its extensive list of site profiles, which reveal the architectural decisions (and revisions) that support Web 2.0 success stories like Amazon, eBay, and Twitter. In this podcast Andrew Glover picks Hoff's brain about scalability tactics like sharding, parallelization, and caching. The two also discuss the challenge of building scalable Web sites that support cloud computing, or service-level architectures, where traffic comes in over APIs. In the end, Hoff gives his insight into why Java isn't necessarily first choice for building sites that scale big, and tips for what to do if you -- like LinkedIn and Fotolog -- decide to use Java anyway.