About this question
Hard · low_latency · Quant Developer interview question · lfence, spectre, memory-fence, low_latency, speculative-execution, x86
In low-latency trading, market data feeds are processed in tight loops where each packet is validated by a sequence number. A CPU's speculative execution engine can bypass this check, creating a Spectre-class vulnerability that leaks data through side-channels. To mitigate this, a memory fence instruction like lfence is used to serialize execution, ensuring a security check fully resolves before any subsequent sensitive data is accessed. Task Implement the function read_guarded(int seq_expected