Microsoft

"You are implementing a hardware-level memory encryption engine for a confidential computing hypervisor running on multi-tenant server silicon": The interviewer challenged me to defend against physical inter-bus probe snooping, cold-boot memory dumps, and replay attacks without introducing hundreds of cycles of memory access latency; I walked through an architecture integrating AES-XTS on the memory controller bus for data confidentiality, paired with an on-die Merkle Tree (Bonsai Merkle Tree) utilizing split counters and Message Authentication Codes (MACs) to detect tampering and enforce replay protection at the cache-line granularity. "An ultra-low latency derivatives exchange needs to compute real-time Portfolio Margin across tens of thousands of complex options positions on every inbound order tick": The panel pushed on why traditional GPU batching fails the sub-microsecond tick-to-trade requirement; I walked through an FPGA-accelerated computing architecture where the Black-Scholes and Binomial Cox-Ross-Rubinstein pricing models are implemented as deep systolic arrays in custom VHDL/Verilog pipelines, streaming streaming-in order ticks directly over a 100GbE QSFP MAC into custom DSP blocks to evaluate full portfolio value-at-risk (VaR) matrices with zero host PCIe transfers. "Design an in-kernel checkpoint-restore mechanism for an exascale supercomputing cluster running parallel MPI jobs across thousands of nodes with non-volatile memory (NVDIMM)": The interviewer asked how to guarantee a consistent global distributed state during a node failure without stalling the entire cluster with a synchronized blocking barrier; I formulated a non-blocking asynchronous coordinated checkpointing protocol, detailing how uncoordinated local NVDIMM page-level dirty logging via page-table entry (PTE) write-protect bits pairs with Lamport vector clocks attached to cross-node MPI communication envelopes to detect and resolve orphan messages and domino rollback hazards.