Upgrade Magento 2.1.* or 2.2.* Version to Latest 2.3.4 Version for site speed and security improvement, You need to follow all the steps given in the articles.
Magento 2.3 Upgrade is a little bit tricky. You can’t just upgrade using only changes in magento/product-community-edition and version line from the composer.json file.
Upgrade using the command line Magento 2.3, Continue reading “How to upgrade Magento 2.2 to Magento 2.3 version?”