There are some other options in between as well. FAISS is a library, so not suited well for production usage unless a single machine is enough. The variety is wider than SaaS vs library. Tools such as Qdrant or Weaviate are Open Source. And Qdrant might be launched without spinning a server, as long as you use a Python client. So you can actually start locally with in-memory mode, run your dev environment on-premise and then prod on Qdrant Cloud, if you prefer.