I'm wary of languages that seek to own the database. In particular, the claim "Coexist with SQL" seems a bit suspect given that e.g. sum types have a custom binary encoding, which likely makes them difficult to interop with from other languages. This makes the claimed interop with other languages really more of a temporary stopping point towards full Acadia adoption rather than a viable long-term equilibrium, unless you e.g. eschew using sum types. (I also suspect that trying to natively support sum types can lead to a kind of FP-equivalent of ORMs' impedance mismatch. The ways I model data with relational logic can be pretty different than the ways I model data with algebraic datatypes and I wonder if trying to force fit the latter into the former doesn't lead to the same problems as force fitting objects into relational logic).

This makes the database closer to something that Acadia compiles to, rather than something Acadia sits on top of. From my own developer experience this feels off, because I generally expect the data layer to be king and application code to revolve around that, rather than having data representation created in code and the database created off that (this is why I also dislike things like ORMs).

In general I view databases as usually having more longevity than application code, especially as you accumulate more data over time. For serious production applications, the database often outlives multiple rewrites of the production application.

I suspect though my concerns are overall rather minor. The ergonomics of the language itself seem enjoyable. Acadia seems like it would be great as an embedded DSL. It's a bit unfortunate that it currently seems coupled to creating an HTTP server. I think that Acadia has greater ambitions beyond just the database, as evidenced by creating a binary web connection with frontend Elm code to presumably obviate the need for encode-decode layers. It seems like Acadia is meant to be a stepping stone towards a closer frontend-backend fusion. But I agree with mjaniczek that something like Lamdera seems a better fit for that.

But given how early Acadia is, I'm still very excited for where it goes. What I've listed is surmountable and I also feel that often a closer frontend-backend fusion might be worthwhile.