How does this compare to https://www.mooncake.dev/pgmooncake? It seems there are several projects like this now, with each taking a slightly different approach optimized for different use cases?

Definitely similar goals, from the Mooncake author: https://news.ycombinator.com/item?id=43298145

I think pg_mooncake is still relatively early stage.

There's a degree of maturity to pg_lake resulting from our team's experience working on extensions like Citus, pg_documentdb, pg_cron, and many others in the past.

For instance, in pg_lake all SQL features and transactions just work, the hybrid query engine can delegate different fragments of the query into DuckDB if the whole query cannot be handled, and having a robust DuckDB integration with a single DuckDB instance (rather than 1 per session) in a separate server process helps make it production-ready. It is used in heavy production workloads already.

No compromise on Postgres features is especially hard to achieve, but after a decade of trying to get there with Citus, we knew we had to get that right from day 1.

Basically, we could speed run this thing into a comprehensive, production-ready solution. I think others will catch up, but we're not sitting still either. :)

FYI the mooncake team was acquired by Databricks so it's basically vendors trying to compete on features now :)