Very good that you are thinking/must think about information encryption. The very first question to be answered is "What is the indisputable reason(s) for keeping information? What is often forgotten is that collecting, storing, protecting, creating regular backups, updating and cleaning up, all those activities costs money and what you don't collect cannot be stolen, and can't be abused.
If you can reduce the information gathering to nothing, the good news is that Google has provided a safe user environment and you are quickly done with the pinnacle of information minimization.
In the event that you have unfortunately come to an irrefutable conclusion that you must collect some personal data, these measures are necessary for a MySQL based solution:
- The MySQL database is encrypted and equipped with best practices security measures.
- The transport between the app and the MySQL database is encrypted and the database only accepts encrypted transport. You can find more information about how to do that here.
What remains is that the use of static passwords should actually be avoided as much. Back to your original question about the Format and Length Preserving Encryption (FLPE) protocol, you could make something that generates the next key, so to speak, that you encrypt information next time.