Senior Developer Interview Checklist: System Design, Algorithms & Behavioral

Senior developer interviews are different in kind, not just difficulty. Mid-level interviews test what you know. Senior interviews test how you think. This checklist is built around that distinction — covering not just topics to study, but how to approach each area with the depth interviewers are actually looking for. The Senior Engineer Mindset Before the checklist, understand what "senior" signals to an interviewer. The shift from mid to senior isn't primarily about technical knowledge — it's about: Judgment under ambiguity — making good decisions with incomplete information Communication clarity — explaining complex systems to different audiences Tradeoff awareness — articulating why you chose X over Y, not just that you chose X Scope awareness — knowing when a problem needs a simple fix vs. a systemic solution Every interview section below should be approached through this lens. Part 1: System Design System design is the primary differentiator in senior interviews. The goal isn't t