Thanks for your reply.
+1 for the example for reading the product using numpy and for the reference to dask. I am sure this will help a lot of people, as it will significantly reduce the memory usage by avoiding snappy ProductIO.readProduct.
After some testing using my MWE, I found that the leak is not restricted to the readPixels method but can even be reproduced when just creating a product using GPF, or merely reading a product using ProductIO.readProduct and then disposing of it again.
Your suggestion to use GPT instead of snappy is a good one. I made a comment on another thread making the same suggestion.
Seems like that is the only solution until the deeper memory leak with snappy can be identified and corrected.