We are using the WP-Optimise plugin (free version) to improve the performance of the site. It provides tools for the following purposes: to clean the database; to compress images; and to cache pages and posts.
To clean the database. The tool clears out unnecessary data, cleans up the database tables and retrieves space lost to data fragmentation. This helps to provide a fast & efficient website.
To compress images. The image optimisation tool uses lossy/lossless compression techniques to convert large images saved in the image library (which can take a long time to load) into more highly compressed files. It enables us to compress PNG, JPG, WebP, GIF, BMP and TIF images. This can help the page load faster and reduce server resources used by freeing up space.
To cache pages and posts. The tool holds our WordPress posts and pages as static files in a cache, from where they can be retrieved quickly without having to run database queries every time a page or post is requested by a browser. This improves the website’s speed and performance. It also reduces the processing load on the web server which helps to improve performance.