>> [...] why supabase went with one of the slowest implementations

> Benchmarks are simply a snapshot in time - [...] it just needs [...] some better indexes

But the choice for IVF-flat indexes was made by the authors of pgvector, and that is one of the reasons why pgvector is slow: O(√n) optimal performance is just not great with large datasets, and this is especially true for the linked list approach chosen by the authors, as it results in large amounts of random IO.

You can't only implement a slow index and then shove the blame of the extension being slow on the index that was chosen by the extension authors: it is an inherent design issue. Sure, those can be fixed, but that doesn't mean it doesn't exist.