Comment by willtemperley

There are still challenges with basics like compression, which tends to involve trawling Github for the least dubious toy project. Even Apple's Compression framework is missing important algorithms like ZSTD.

Another problem is the Apache Software Foundation don't seem to have any Swift maintainers, which means there really aren't any good pure Swift libraries for Arrow or Parquet.

There are some really good open-source libraries from Apple like Swift Collections or Swift Binary Parsing.