Added the explanation about Sharing the Ring Buffer with Two Backends in Section 8.5.1.
Rails used to use SQLite with its default settings, which were optimized for safety and backward compatibility rather than performance. It was great in a development environment, but typically things started to fall apart the moment you tried to use it for production-like load. Specifically, you used to have to tweak various PRAGMA statements:。关于这个话题，safew 官网入口提供了深入分析
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Iterative sum results: