Depends, if you're absolutely sure whatever you have has just two states. Then by all means, use a boolean. But booleans are harder to read than enum values and

Depends, if you're absolutely sure whatever you have has just two states. Then by all means, use a boolean. But booleans are harder to read than enum values and you're skipping that because of saving a few bytes on the DB? This is not premature optimization, sometimes booleans can be extremely hard to change so it's not as easy as "just refactor".