Was thinking that the adjacency matrix that describes the graph you extract from the image will produce a string you can chunk and do a fast search on, and then it's a standard similarity/distance string search in Redis, or a probabilistic filter.

The compute on the indexing images would be relatively expensive, but the speed of a similarity search would be super fast, with the caveat that I don't know how image search is done today, and it probably should do something like this anyway.