How long outside academia without publishing is too long? I finished a PhD in Earth Science 10 months ago and now work as a software engineer. I haven’t done any research or published in these 10 months. Is it too late for me to go for a postdoc and have a realistic shot at tenure track? My PhD is from a good school in our field and I have a good publication record in top journals in our field.
You should be getting advice about such things from your advisor and/or other experienced colleagues within your academic field. It’s hard for anyone here to make predictions about whether you can get a postdoc based on so little information. 

In general though, I would say 10 months isn’t such a long time, so if you were in a good position to get a postdoc 10 months ago then it shouldn’t be very different now, assuming you are on good terms with your advisor and other people who can write you letters. And who knows, the skills you developed in your software engineering job might even come in handy in academic research. Good luck!