when should I use cookie-parser with express-session?

For future humble coders, that will stumble upon this – I’m posting an up-to-date answer:

As the official description of express-session middleware says here: express-session

Since version 1.5.0, the cookie-parser middleware no longer needs to
be used for this module to work. This module now directly reads and
writes cookies on req/res. Using cookie-parser may result in issues if
the secret is not the same between this module and cookie-parser.

Therefore, just use express-session middleware and have a nice day.