Here's the Google engineering ladder:
SWE 2 (fresh college graduate)
SWE 3 (fresh PhD or 5+ years experience)
Senior SWE (manager-equivalent; first acceptable "terminal" level.)
Staff SWE (serious engineering chops)
Sr. Staff SWE (rare; candidate for Director/Principal)
Principal SWE (Director-equivalent)
Distinguished SWE
Eng. Fellow (VP equivalent)
I'd say that 5% of SWE 2-3 are Real Googlers, 35% of Senior are, and 85% of Staff are.Real Googler means you have freedom of the castle. If you want to work on Search, you work on Search. If you want to dedicate the next 6 months to the maintenance of a module on which your work depends, you do it. It's like an open-allocation environment, and similar to what Google was before it got Too Big.
Below the Real Googler Line, you actually sweat performance reviews because your manager can unilaterally reduce your credibility to zero. Above it, projects and managers compete for you. There's probably some room for play (when you're slightly above RGL, you might still worry) but it has a binary feel to it. When you're a Real Googler, you have independent credibility. You don't sweat Perf.
Traditionally, the RGL was the Senior SWE tier. That was the level at which you were trusted to choose projects, and even manage if it were needed.
You're expected to make Sr. SWE in 3 years from SWE 3 and 5 years from SWE 2. If you don't, it's like being denied tenure and your project options (which probably weren't great, since 99% of getting promoted is getting on the right projects) continue to decline.
If you have Real Googler credibility, you can get away with a lot. There are people who start strong and get promoted, then go along for 3+ years without committing any code before they get fired. That's what RG gets you: a 3-year audit cycle. On the other hand, if you're not above the RGL, while it's not technically speaking hard to stay employed, it's extremely competitive to get into a position where you can have a real impact.