Software engineer

You spend a summer writing real software for a trading firm, on a project built around what one of its engineering teams needs right now. Jane Street trades in financial markets and writes most of the software it runs on. As an intern you are paired with full-time software engineers who act as your mentors. They design your project from their team's current work, and the code you write is meant to reach production, which means the firm actually uses it once it is finished.