The alternative is to find solutions that can reasonably support different requirements because business needs change all the time especially in the current state of our industry. From what I’ve seen, OSS Postgres/pgvector can adequately support a wide variety of requirements for millions to low tens of millions of vectors - low latencies, hybrid search, filtered search, ability to serve out of memory and disk, strong-consistency/transactional semantics with operational data. For further scaling/performance (1B+ vectors and even lower latencies), consider SOTA Postgres system like AlloyDB with AlloyDB ScaNN.

Full disclosure: I founded ScaNN in GCP databases and am the lead for AlloyDB Semantic Search. And all these opinions are my own.