I wonder why Singlestore has been so unpopular (at least I never hear about it). Quick guess is that HTAP itself isn’t a significant feature requirement, maybe just a cherry on top of other major db features.
In addition to the AI use cases, sometimes you wanna share the data warehouse data in oltp way for fast lookups and high concurrency. Not sure whether Neon will do that but I hope so.
One example from Snowflake is hybrid tables which adds rowstore next to columnar.