Looking for Security expert - Storing encrypted data

I am looking for security expert to suggest what the practices of storing encrypted data on the database. Scenario: User on the browser would authorise their github (example provider) to us via oAuth. I would get their token and save in the database. Token need to be encrypted before saving into database but what the best practice/tools to do this? I have came up with two options: 1. Using Halite script (PHP / libsodium) and then store into MySQL database. 2. Using Vault by HashiCorp and the Vault database could be hosted on S3 Bucket for example. You have to consider if a website ever get hacked, need to find a way the hacker would have difficulty to decrypt the tokens. We need some kind of extra security layers. My current Environment: NGINX, PHP 7, MySQL and hosted on Digital Ocean.