FPC cache possibly preventing Amasty One-step Checkout from changing Country selections, and possibly unable to clear cache under certain conditions? · Issue #336 · GordonLesti/Lesti_Fpc · GitHub
Magento用のページキャッシュプラグラインでパフォーマンスアップ | Webエンジニアブログ
Redis Configuration for Magento 1.9.x - GetPageSpeed
Magento 1.9 Performance Checklist | by Danila Vershinin | Medium