I'm leaving my first job out of college for something else, and when I left, the CEO (small company) said that their door is always open if I ever want to come back. I saw this as an exceptionally positive thing, but also assumed it was common at this particular company because it is a small company of very niche expertise and so someone they have already trained for two years would be a valuable asset to hire back later.
I mentioned this to someone who works at a much larger and much less specialized company in essentially the same field (we are both software developers so there is a wide range of job types in our field). He told me that every company tells this to departing employees and mentioned that at his office (a small subset of many contractors from different companies working together), they have said the same thing to departing employees.
That office does have a high turnover rate (much like the job I am leaving), and they work on specific in-house developed software that takes awhile to learn the ins and outs of. Apart from a couple of managers, they don't have a lot of developers that have been there long enough to really be deep experts. So I think it does make sense that that office would want to hire old people back, but the company is a separate issue and the office and the company would need to coordinate. Either way, I think I understand why that would be a common sentiment at that particular office (but I think it would be strange for the company itself which is large and tends to hire generic developers).
Is this true of every software development job? If I left a job at Amazon or Google, would they "save my spot" in case I wanted to come back later?