When things go seriously wrong in a well-built but complicated system, the cause is often a cascade of small failures that pile up. Not that we’re building rockets over here, but an excellent example is the ill-fated Ariane flight V88. Solving the issues behind such failures can be problematic. Many things contribute to the difficulty, from the extensive use of caching to the need to convincingly reconstruct the failure in retrospect. Debugging this kind of failure, especially under pressure, is hard. We consider the ability to do this to be the hallmark of a senior developer. Even so, it is essential to have a team of experts working together to troubleshoot issues and find solutions promptly to help keep your site running.