This question evaluates understanding of cache-efficient, high-throughput hash lookup design and related competencies such as hashing strategies, probe behavior, memory layout, vectorization, bitwise optimizations, prefetching, alignment, and microarchitectural performance trade-offs.

Design a high-throughput hash-based lookup to be called inside a tight kernel. Choose between open addressing and chaining, specify the load factor, probe sequence, and table layout to favor vectorization and contiguous accesses. Show how to use bitwise operations, prefetching, and alignment to reduce collisions and cache misses. Explain trade-offs and how you would profile and validate the design.