No, I'm not questioning whether or not it was a caching issue. I'm taking exception to the lack of accountability. They chose the library. They (probably) chose to ignore a documented or common failure mode of caching systems through either poor choice of key or lack of synchronization. They've obviously designed their infrastructure in a way that isn't resilient to its current level of usage (cold start is a normal part of software's lifecycle).
They could have chosen to own that, but instead they blamed everyone else. That's not a sign of a trustworthy service provider.
