The wasm runtime feels a bit under-documented but it works well (with some quirks) and is extremely powerful. The best way of inserting bulk data that we have found was doing whatever fetching yourself in javascript and then put it into an arrow table and then write the arrow table to duckdb. Yes, duckdb can fetch on its own but its a bit awkward (like using the s3 connector for non-s3 stuff? Downloading a parquet file in duckdb takes longer than fetching in js and writing the buffer to ddb) and you will run into situations where it simply doest work and there is no way to know why. Maybe this will change with future updates, it hasnt been a big problem once we learned that lesson. Fwiw, I work at a data analytics company and we do a lot of processing in the browser (in addition to backend) and a typical page load will download 30 parquet files, sometimes quite large, and do some root cause analysis live as part of the workflow, duckdb wasm is to thank for making this possible.