Microsoft

"Suppose our database storage engine crashes mid-transaction during a power cut": The interviewer asked me how to guarantee atomicity and durability without flushing every disk block synchronously; I walked through implementing the ARIES recovery algorithm, breaking down write-ahead logging (WAL), physiological logging, and the three-pass sequence (Analysis, Redo, Undo). "You're writing a compiler optimization pass for an instruction set with only 8 general-purpose registers": The task was to map an intermediate representation with hundreds of temporary variables onto limited physical hardware with minimal memory spills; I framed the problem as graph coloring register allocation on an interference graph, using Chaitin-Briggs heuristics to identify Kempe chains and spill candidates. "Consider a real-time multiplayer game server that needs to broadcast player positions only to opponents within vision range": Rather than doing an O(N^2) pairwise distance check across thousands of concurrent players every tick, I designed a spatial partitioning scheme using a Dynamic BVH (Bounding Volume Hierarchy) paired with loose Octrees, explaining trade-offs against regular grid spatial hashing when entity distribution is non-uniform.