Milvus is completely open source (https://github.com/milvus-io/milvus) and supports a variety of index types (https://milvus.io/docs/overview.md#Index-types) and support various consistency levels, scalar/metadata filtering, and time travel. We started working on Milvus back in 2018, with 2.0 being released in January 2022 (https://github.com/milvus-io/milvus/releases/tag/v2.0.0).

For those interested, here's a comparison with other open source vector databases: https://zilliz.com/comparison. For those who don't want to be burdened with installing and maintaining a local database, there's a managed service available as well: https://zilliz.com/cloud.