Solving magento slow frontend problem when there are active processes on the backend database

The databases are sometimes slow. On my site I have installed FPC and other modules. The site is fast. i Use cloudflare, page speed, redis and other modules. But when I work in backend or when cron jobs are active the site becomes very slow in the frontend. For example, if i work on the M2EPRO module on ebay listings, the site becomes slow both in the frontend and in the backend