Documentation in a consumable format does not exist here, it will cause you issues.
Code base is monolithic, expect to see lots of mess due to people not wanting to impact it, improper use of modern coding concepts, compounds with the documentation issue.
Most applications are simple or could be simple but due to the above simple problems become difficult.
You'll see a lot of ways not to do things, learn from the past generations mistakes, you'll grow a lot, many people work hard to keep things working.
Opportunities for job promotion or career growth is not defined even if you directly ask management.
If you're someone who can't make decisions for themselves, this place isn't for you, people hiding behind tickets/meetings/emails make things more difficult than needed.