tbh. Looks like a huge overengineered legacy project. What is the clue to having all these ANN indexes in place? Is it a kinda art collection? What is the sense when you can just have HNSW in memory, with quantization, or on disk, GPU accelerated, etc. There are already better alternatives like Qdrant, which is written in Rust and super performant
https://github.com/qdrant/qdrant, or Weaviate with GraphQL interface
https://github.com/weaviate/weaviate