First, your co-worker is officially your enemy. Expect to be stabbed in the back. Some will say they will help you and tell everyone else how much they are helping you, but then will actually do barely any actual work to deliberately undermine you. Other people will talk badly about you. Others will take credit for your work, possibly your own manager. Most people are good honest folks, but watch out for the bad ones. Especially be watchful for managers who were forced to get themselves promoted out of whatever it was they originally did very well. This is well beyond the normal level of office politics. Your first years will seem great but problems compound over time.
This is a result 3 things:
1. The performance review system is a forced curve. 10% of all employees will be graded at the bottom rung and put on "probation" or "corrective measures". Thus, if you do well but are on a team of 10 great employees, you will be in the bottom 10%.
2. You must move up the corporate ladder ("you are expected to grow"). Otherwise, you will be forced out of the company. Even if you are incredible at what you do and love it, you must move up (ex: great SDETs must become managers, sometimes lousy managers).
3. Promotion velocity: if you don't move up the corporate ladder fast enough, you will soon become unpromotable regardless of how well you perform.
Second, technical ability is not valued as much as management ability. If you love to code, expect to find less and less time to code as you do more management of either other full-time employees and/or contractors and/or vendors. Contractors and vendors do much of the technical work these days.
