Performance decrease after migration from 2.1 to 2.3

[dpolan]

Hello,

We have developed an eCommerce with Magento 2.1, using it only as a REST API through or web application.

Recently, after we upgraded from 2.1 to 2.3 version, we are experiencing long TTFB delays on every request we made to the API (more than 4 seconds).

We have tried lots of approaches from database query checking to test requests inside the server local network but did not find the root of the issue yet.

Any ideas on how to fix this kind of issue?

Kind regards

[theMageComp]

Hello

General recommendation from my side.

Any third party extension? Can you disable all and check once?
Check in Gtmetrix and pingdom, if developer hired then ask him to try developer debug tool once. Check hosting performance from hosting guys, try the same setup in another hosting too once.

[jay_baher]

One of the reasons of this problem can be a high number of requests. After reducing this number website performance is better. 

So, here are possible solutions to your problem:

• optimize a number of requests, the logic of their building, the parameters of their executing;
• update the modules on your server;
• configure the database (some memory settings, qwot, something like this);
• change server - increase the limit of default memory, the processor power.

If you have questions about Magento performance optimization, feel free to ask.