SQLite and DuckDB solve different problems and actually complement each other quite well. SQLite is excellent for transactional workloads (OLTP), while DuckDB shines for analytical workloads (OLAP), especially time-series data and aggregations.
We’ve been using both side-by-side in an open-source project for about two years: SQLite for configuration and transactional data, DuckDB for historical sensor data and analytics. So far, it’s been a very good combination.
I can see applications having valid reasons to use both. You can use SQLite as the catalog in duck lake systems, for example. SQLite is your metadata record, DuckDB is your ingestion/scanning/aggregating/joining engine.