> It's hard to believe fixed width files are still being used today. Parsing these kind of files with 45 million records, each 600+ bytes is a huge pain. I chuckle when I think about the first time I dealt with these files and thought I could open them in an editor...

Depending on the business-application, fixed-width formats are fantastic because they allow for genuine O(1) random-access to records without needing to precompute an index first. Writing parsers for fixed-width formats is also much simpler, for example, because it eliminates ambiguity around null-terminators vs length-prefix in text/string/array data - for resource-constrained environments it's great because you can guarantee you won't need to dynamically-allocate buffers. I feel the only real arguments against fixed-width records are concerned with wasted space - which are mitigated if your system lets you compress them somehow - because they'll typically compress very, very well.