apoc.load.csv is your new friend if it's a new database or one who needs to be updated.
It's explicitly build for your use case, and it won't fear your tiny 500 000 lines.
Be aware that you must always create constraints before importing any data with a MERGE OR MATCH clause, or your children will die before it's finish.
I used Python before for my data injection, now I use apoc.load.csv to standardize and improve the speed of the process.