They recently rolled out the Booking Career Framework, creating itemized lists on the expectations for each level, so I know what it takes to get promoted. I'm 70% - 80% that I'll get it in the next performance review cycle, but I have some concerns.
My main concern is that Booking doesn't have a lot of space to grow, evident by the fact that I spend ~50% of my time on the company's migration effort to move from Perl to Java. The effort for this started in 2014 and is around 30% done. It's not a super high company priority according to my manager, but my team spends a lot of time on it, which worries my prospects about finding scope with better business impact.
On the flip side, I had Java experience coming into Booking, so I am well-equipped for this migration work. For example, I was able to solve a deep image loading issue recently that required a strong understanding of default Perl behavior.
Alex's answer is awesome and comprehensive already.
If i would add one more point is that, for SWE1 -> SWE2, you can heavily leverage your manager to give you clear guidance.