I use JSON streams a lot with command line tools. Keep in mind that it’s limited in that each object must consume a single line. This allows you to recover from

I use JSON streams a lot with command line tools. Keep in mind that it’s limited in that each object must consume a single line. This allows you to recover from syntax errors in a single entry; each line is a fresh start. Have you considered SQLite? I know it’s not a friendly text format, but it alleviates a lot of the issues with the “append to a text file” approach, such as concurrency. It’s great for this sort of thing.