duckdb query takes too long to process and return inside Flask application

I have a Flask app and want to use duckdb as a database for several endpoints. My idea is to query the data and return it as a .parquet file. When I test my database with a simple Python script outside of the Flask app, it can query the data and save it as a .parquet in under a second. When I bring that same methodology to the Flask app, it still successfully queries the data and returns it as a .parquet file but it takes roughly 45 seconds. Other endpoints that return a .parquet file -- ones that are pre-staged and do not need to be queried -- can do so in just a second or two. So the issue, apparently, is incorporating duckdb inside my Flask application. Here is a sample boiler plate of what I have:

@test.route('/duckdb', methods = ['GET'])
def duckdb_test():

    con = duckdb.connect(database = '~/flask_db/test.db')

    # get tempfile .parquet
    tmp = tempfile.NamedTemporaryFile(suffix = '.parquet', mode = 'w+b', delete = False)

    # get data
    df = con.sql("SELECT * FROM tbl WHERE name = 'John'").to_df()

    # write to temporary .parquet
    df.to_parquet(tmp.name, engine='pyarrow', index=False)

    return send_file(tmp.name, mimetype='application/octet-stream', as_attachment=True, download_name="request.parquet")

I want to save it as a temp file. Not really sure what's wrong here. Again, it does work, but it just takes way, way too much time. The data being returned is about 12,000 rows in a ~5.5M row database -- but given that it works fairly quickly outside of the Flask app, on the same VM, the size itself shouldn't be an issue.

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