Common Site Speed Issues for Magento
I was responding to a question on Reddit this morning and thought our readers might benefit from a cross post here.
Original question: What could cause a suddenly slow Magento 188.8.131.52 and what to do?
Big asset - if you’ve added an image that is too large, you may have done it to yourself. This is easy to see either by using the element inspector in the browser, or, you can use Google’s Page Speed Insights. Usually, this will only affect one page (often the home page slider), but, it is a VERY common issue. You may want to consider a CDN like CloudFlare that resizes images for you so you don’t have to worry about it.
Holiday traffic - are you reaching server limits with cyber-Monday or black Friday sales? If you have Google analytics installed you can check concurrent users.
Database limits - if you have separate servers for the db and the application, you may have hit some storage, or, even I/O limits if your host has a throttle on that. You should be able to ask your host. Some extensions are notorious for blowing up the database. Once you start hitting one of those limits on your DB server (probably memory or storage), it will limp along or even stop working altogether.
Holiday traffic through your host - given your comments about your CPanel in responses to other comments, I’m assuming you are NOT on a cloud (AWS, Google Cloud, Azure, etc). You might be in a multi-tenant setup. If so another site on the same server may be getting pounded (or your data center as a whole if it is small or capacity-constrained) to the point that network is too slow. You can contact your host about this one. In your GA there is a site speed section. Normally, it is not very helpful, but, if your TTFB (time to first byte) has increased recently, this could be the issue.
Bot traffic - Unfortunately, this is becoming a common issue. When a nefarious crawler bot detects a new Magento site, it starts hitting it, looking for weaknesses to exploit.