First, what is the AlloyDB columnar engine?

The AlloyDB columnar engine is a built-in, in-memory cache that automatically stores frequently queried data in a specialized, scan-optimized columnar format. It allows AlloyDB to handle heavy analytical queries up to 100x faster than standard PostgreSQL. Additionally, it accelerates ANN searches by storing the index in memory, using a vectorized memory layout for fast traversals, and bypassing standard PostgreSQL buffer manager overhead.