High load has four usual causes. The Graphs and Traffic tabs tell you which one in a couple of minutes.
- Confirm
Graphs, Live: CPU near the maximum and the 1-minute load above the number of vCPUs.
- Bots?
Traffic tab of each application: one address or user agent with thousands of requests, or a high bot share. Block the worst (Block) and set the browser check to Filtered pages for an hour.
- Cron or indexers?
Peaks at fixed times: Magento indexers on Update on save, a full reindex every hour, an import job. Move heavy jobs to the night.
- A slow page?
PHP slow requests log: the same function again and again points to one module.
- Real customers?
A campaign or a peak that is good news. Enable Varnish, check the caches, and consider a bigger server for the season.
With automatic mode on (the default), the browser check already starts on filtered pages when the load goes above 1.5 per CPU, and stops 30 minutes after the server calms down. See the browser check.
Did this solve it? If not, tell us what you see and we look at your server.
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