Hey thanks for checking this out. So I was able to get some significant performance improvements, but it's still a bit slower on the large EC2 than on my workstation:

def extract_many_postfiles_to_df(
    run_id: int,
    file_paths: list[str]
) -> pl.LazyFrame:
    """Generic function to extract data from PLOTFILE, POSTFILE,
    MAXIFILE, RANKFILE, EVALFILE, SEASONHR, MAXDCONT, MAXDAILY, 
    and MAXDAILYBY-R

    Args:
        run_id: database ID of the run
        file_paths: path to the output file 
        output_table_types: POSTFILE, PLOTFILE, etc.

    Result is returned as a string-only df with headers consistent with AermodResult
    db model
    """
    concatenated_file = tempfile.NamedTemporaryFile(delete=False)
    concat_files_with_header(
        file_paths,
        concatenated_file.name,
        start_from_line_num=9
    )

    with open(concatenated_file.name) as f:
        split = list(islice(f, 8))
    colnames, widths = _extract_output_file_headers_widths(
        split[6],
        split[7]
    )
    colnames = [_POSTFILE_COLNAME_MAPPING[c] for c in colnames]
    df = read_output_file_from_disk_polars(
        concatenated_file.name,
        colnames,
        widths
    ) \
        .with_columns(
            output_table_type=pl.lit("POSTFILE"),
            run_id=pl.lit(run_id),
            averaging_period=pl.when(
                pl.col("averaging_period").str.contains(r"^[0-9]+$")
            ).then(
                pl.col("averaging_period") + "-HR"
            ).when(
                pl.col("averaging_period").str.contains(r"^[0-9]+$").not_()
            ).then(
                pl.col("averaging_period")
            ), # Converts numeric only averaging pd to text (e.g. '8' to '8-HR'),
            ranking=pl.col("ranking").str.replace("[^0-9]+", "").cast(pl.Int32) if "ranking" in colnames else pl.lit(0),
            occurence_datetime=(
                    pl.col("occurence_datetime").fill_null(
                    datetime(1969, 1, 1, 1).strftime("%y%m%d%H")
                ).replace(
                    "0",
                    datetime(1969, 1, 1, 1).strftime("%y%m%d%H")
                )
                    .str.slice(0, 6)
                    .add(
                        pl.col("occurence_datetime")
                            .str.slice(6, 7)
                            .cast(pl.Int8)
                            .sub(1) # Subtract 1 from datetime hour so it can be parsed with the %H format
                            .cast(pl.String)
                            .str
                            .zfill(2)
                    )
                    .add("00")
                    .str.to_datetime("%y%m%d%H%M")
                    .cast(pl.Datetime)
                    .dt.truncate("1s")
                    .dt.strftime("%Y-%m-%d %H:%M:%S") # truncate 1s allows clickhouse compatability
            ) if "occurence_datetime" in colnames else pl.lit("1900-01-01 00:00:00")
        ).cast({k: v for k, v in _POSTFILE_DTYPES.items() if k in colnames})
    LOGGER.debug("read all output file texts into polars")
    LOGGER.debug(f"file loaded to df: ")
    return df