Database / DuckDB Interview questions
What is the httpfs extension used for?
The httpfs extension lets DuckDB read (and, for some backends, write) files directly over HTTP/HTTPS and from S3-compatible object storage, without first downloading the entire file to local disk.
INSTALL httpfs; LOAD httpfs; SELECT * FROM read_parquet('s3://my-bucket/data/2026/*.parquet');
For Parquet specifically, this combines with DuckDB's ability to use file metadata and statistics to fetch only the specific byte ranges actually needed to answer a query, using HTTP range requests, rather than always pulling an entire remote file across the network. This is what makes querying selectively against large remote datasets in cloud storage practical without local staging, since the amount of data actually transferred can be a small fraction of the total file size for a sufficiently selective query.
The httpfs extension enables DuckDB to:
For a selective query against a remote Parquet file, httpfs can:
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