My website is loading very slow, I am facing this issue since quite a long time. Suddenly all works properly and then suddenly website loading time goes to 30-40 seconds. quick fix is that if I Truncate core_url_rewrite db, the website starts opening in normal speed like 3-4 seconds, but some of the pages doesn't work so for them to work I need to reindex catalog url rewrite, then again it will start working slow. I hardly have 15 mb of core_url_rewrite db size. My total products on website is 5-6k. This issue suddenly started happening after we planned to upgrade to Magento 2 and the developer who was working on this had already finished the pre-migration process and left the project in half way. Due to his migrations there are some M2 tables created in our live database. We also upgraded our server to 8GB ram , 240 Gb HDD & 8 CPUS. Still this issue didnt resolve. Please if anyone can help me out on this.