[goog_throwaway]

When I left Google I was told I could come back within a year and not have to go through the full interview process. Just a few rounds of calls with recruiters a hiring manager. They apparently do this for anyone who goes out with high performance ratings on their last perf (Exceeds Expectations or greater).

Not a grace period per se, but pretty nice.

[throwaway-1209]

Yes you could, but there's no guarantee whatsoever they actually will let you come back. It's a subtle point which many people don't understand. The first part, them deciding to let you come back, is not deterministic. The second (no interview if you didn't suck before you left) is. I know several xooglers who went back (in one case 3 years after leaving, no interviews). I also know several who got their applications chucked into /dev/null, in spite of being kickass engineers and good people in all other regards.