Chris M.

The Debug Bar Query Tracer plugin backtraces all calls to <code>WPDB::query()</code> and determines:
<ul>
<li>which plugin caused that database query (it ignores all queries that are a part of normal WordPress activity), and</li>
<li>the function chain that led to that query. </li>
</ul>
It then displays that information on an additional panel in the <a href="https://wordpress.org/extend/plugins/debug-bar/" rel="ugc">Debug Bar</a> 
plugin (which is required).

Debug Bar Query Tracer

A Debug Bar plugin that lets you trace what plugins are causing database queries.

jamesdlow

BETA: Extend WordPress with MySQL database read replica support for greater speed and scalability 
This is a first release beta, and should only be used at your own risk

Database Read Replicas

BETA: Extend WordPress with MySQL database read replica support for greater speed and scalability

Debug Bar Query Tracer vs Database Read Replicas