1 vector against 1 million vectors in 768 dims at k = 10 takes 259 ms for me using Faiss CPU IndexFlatL2 with Intel MKL:
https://gist.github.com/wickedfoo/165b69075cfcceba872aec1c46...
https://gist.github.com/wickedfoo/165b69075cfcceba872aec1c46...
I like how you tested "query multiple vectors at once". Super useful when documents can be batched, for increased throughput. If I'm reading your benchmark correctly, Faiss brute-force can do a batch query of 10,000 vectors in ~19 seconds => 1.9 ms per vector.
That's pretty cool – and more than 130x faster than querying those 10,000 vectors individually, one by one.