Applying at the big G? Better learn about the caste system.
Thinking about working at Google? You need to be aware of the caste system. Here's how it's implemented.
There is an entire class of jobs which are published as "google.com" or similar on the public site. These refer to SRE, aka Site Reliability Engineering. This is a term which has since been recycled at other companies, but it seems to have started there.
Here's the rub: there are two flavors of SRE. One is a "SA-SRE", and the other is a "SWE-SRE". You'll be told that there's no difference, but that's a lie. There is a huge difference which will only become apparent after you've decided to transfer.
You see, a "SA-SRE" is a sysadmin role. It's what they call the "O" ladder. People on that ladder can only go to other "O" ladder jobs, and that means other sysadmin jobs. Guess what. Most of the internal transfer opportunities are not SA jobs. If you go to that site (compass, magnet, whatever they call it now), you won't see many opportunities.
Meanwhile, the so-called identical "SWE-SRE" is a software engineer who just happens to also be a SRE. They are on the "T" ladder, and they can transfer out to any other job on that ladder. Those are the majority by far. If you want to go work on the latest ShinyThing project which involves programming, odds are it will be a SWE / T ladder job.
So let's say you find yourself in this O ladder job and you want out. Instead of just transferring out in a reasonable amount of time (a couple of weeks, perhaps), you now have to go through an internal job ladder transfer process.
Prepare for the ultimate insult. Now's the point where you get to interview for your own job. Yep, odds are you have already been writing code and doing SWE type stuff before you decided to move on and make it official.
At this point, they will dig up a few higher-level people and get them to run you through the wringer with the usual "what's the complexity of a foo sort, or a bar sort" stuff. You will wind up feeling very very small by the end.
If you make it through the process, you'll migrate from O to T and will be able to transfer out to many other jobs. Congratulations! You are now better than those dirty, dirty sysadmin types.
Source: my own wretched experiences.