Hi @EduardoHitek and welcome! Since your code doesn’t contain these parts (and also no example JSON file) we can’t try whether any changes affect memory usage.
Please don’t add these files but instead minimize your code to the extent possible while still showing the high memory usage, as recommended by the the question guidelines:
It would be great if you could post the smallest possible code samples that allow people to see what your problem is.
For reference, here is an older post about debugging performance problems:
The crucial point was that it contained code that was runnable out-of-the box and that we could experiment with.
I assume the size of the file comes either from a big transactions array, or from processing multiple bank-statements (you should include the code calling your template as well).
Instead of reading a JSON-file, you can include the test data directly in the code:
#let single-data = (created_at: ..., ...)
#let data = 100*(single-data,)
This creates a 100 element array of duplicated test bank statements. Please confirm that your test data shows the high memory usage, so that when we copy your code we can reproduce your problem directly.