Microsoft

"You are designing the virtual memory manager for a microkernel operating system running on a modern 64-bit architecture with 5-level paging (Paging57)": The interviewer challenged me to handle translation lookaside buffer (TLB) shootdowns across 128 cores without cascading inter-processor interrupt (IPI) storms; I walked through an implementation using hardware-assisted broadcast invalidation, batched asynchronous shootdown queues with generation counters, and opportunistic lazy unmapping for non-critical user-space regions. "An automated satellite constellation requires dynamic inter-satellite optical laser routing under continuous orbital motion and line-of-sight dropouts": The panel asked how to calculate optimal multi-hop paths without flooding the constellation with routing updates; I modeled the network topology as a deterministic Time-Expanded Graph (TEG), utilizing Contact Graph Routing (CGR) and an interval-based Dijkstra variant that pre-computes transmission windows and buffer delay bounds across non-stationary orbital planes. "Design an out-of-order execution pipeline's load-store queue (LSQ) for a superscalar RISC-V core that handles memory disambiguation": The interviewer asked how to resolve speculative load instructions before the physical addresses of preceding store instructions are known; I detailed the architecture of a partitioned Load Queue and Store Queue with associative CAM lookups, walked through store-to-load forwarding using byte-mask masking, and explained recovery mechanisms via pipeline flushes using memory order violation predictors when misspeculation is detected at store retirement.