Async programming is not easy. For example the following line

    for await ...

will will process the whole file, then give you all lines at once.

So the problem is probably that all lines in all files are parsed at the time creating a bottleneck somewhere and ballooning memory usage. The solution is to use streams, pause the stream in order to parse the line, then continue the stream. And pipe the parsed result to stdout or a tcp stream. That will use minimal memory, and if the GC doesn't do it's job Node.js now supports manual GC. So you could probably parse the whole thing using only a few kilobytes of memory.