Note: Although the levels may be different, these tend to map pretty cleanly to similar hierarchies at Google and Microsoft, but they have no correlation to hierarchies outside of the "club" of elite companies (Microsoft/Amazon/Google/Facebook, etc. on the west coast, Bloomberg/Goldman/HFT firms, etc. on the east coast).
People with 10-15 years of software engineering experience interview all the time at these companies, but they may not be fit for much more than a junior engineering role (SDE I or SDE II, depending on which company you're looking at).
- Is essentially a new and inexperienced (below the level of Amazon/Microsoft/Google engineers) junior engineer.
- Attending college for computer science, or really good at teaching themselves from books and online tutorials.