Optimize WordPress Backend Performance -- 2

My WordPress site https://ums01.co.jp/refleshed-berverage/ feels snappy on the front-end, yet the server is taking too long to assemble the page. The priority is clear: cut backend processing time so visitors receive content far faster.

The work centers on three intertwined areas:
• Plugin performance – audit active plugins, remove or replace heavy ones, and refactor any custom code that slows execution.
• Database queries – profile slow queries, add or adjust indexes, and fine-tune wp_options or autoloaded data to reduce query count and execution time.
• Theme code – streamline template files, eliminate redundant functions, and ensure hooks run only when required.

I already handle basic caching and asset minification; the bottleneck lies deeper. Please benchmark before and after (Query Monitor, New Relic or similar) so improvements are measurable—ideally cutting server response time by at least half under typical traffic.

Deliver the optimized codebase, a concise change log, and a short report explaining what was done and the new performance metrics, so I can maintain the gains moving forward.