mysql error on docker-compose

[Adrian-Sanchez]

I was getting this error

Can't create/write to file '/var/lib/mysql/is_writable' (Errcode: 13 - Permission denied)

Got it working by adding user to the .yml file

db:
image: mysql:latest
container_name: "cb_database"
user: "1000:50"
...

Only thing is, I don't really know what it does and if its recommended.