Causes of 504 Gateway Timeout error in wordpress + woocommerce shop?

Question

Electronic commerce

Hello.
If in order, then I installed the wordpress system on the VPS hosting , then the woocommerce plugin - woothemes.com/woocommerce/, then the Saphali Woocommerce Import plugin - saphali.com/woocommerce-plugins/woocommerce-import-products-from-csv-price-list to add wholesale products.
After setting up the design, I uploaded the products through the import plugin mentioned above. After some time, I collected all the price lists from suppliers and updated the available / not available and the prices of all goods (about 6000 pcs). After that, the site began to "respond" for 30-60-90 seconds. Previously, the response speed was 1-5 seconds (with caching plugin disabled).
Retreat. This situation has already happened on another hosting (not vps). In search of a reason, the site moved vps. But the problem was not solved - the pages loaded for 1 minute, and often longer, which ultimately led to the 504 Gateway Timeout error. Hosting technical support reported that the site system loads the entire processor and RAM in cases where I perform some actions in the site admin panel (for example, delete one product, change the status of the product to draft). In the end, I deleted everything to hell and repeated the procedure described in the first paragraph again.
There is one moment, I updated the woocommerce plugin, updated the wordpress when it was offered in the admin panel. I thought that the reason for the brakes in this. Then I rolled back the site to woocommerce and wordpress updates. The brakes stopped, but after adding new products, updating the balances through the Saphali Woocommerce Import plugin, the problem with the brakes recurred and is still relevant at the moment.
The state of the RAM at the moment when the speed of the site is very low.

I can assume that the problem with loading the site is not related to adding and updating products through the import plugin. Perhaps this is a coincidence. I am not able to understand the reason, given the superficial knowledge in this area.
Link spickandspan.ru

Answer 1

And what are the characteristics of your vps?
In your case, there are two solutions:
1. Find a person (or yourself) to optimize the system.
2. Take a more advanced vps.