You’d be (pleasantly) surprised how easy it is to copy a postgres database. It literally copies the data files for the database to a new directory so the operation is relatively quick if the total volume of data is not large.
What’s more challenging is handling many concurrent connections as a different database would mandate a separate connection and you can’t perform any meaningful connection pooling.
That's accurate! Another bottleneck we have is Mathesar-level state management. We keep some state to reduce redundant Postgres queries. During most of development we focused on single-database use cases, but for the demo we had to expand to managing state for multiple databases in as isolated way as possible. That forced us to face some technical debt in assumptions we made about our state and how we organize it. State-related technical debt is the most challenging, imo.
What’s more challenging is handling many concurrent connections as a different database would mandate a separate connection and you can’t perform any meaningful connection pooling.