You shouldn't use Electrum to import 200k private keys. Bitcoin Core will probably have problems too.
Fortunately it's not true for Bitcoin Core. Looking at
this thread, some users report they can import million private keys into wallet.dat. Although you need lots of RAM, since Bitcoin Core apparently load entire wallet.dat content into RAM.
Maybe it's easier if most of the keys aren't funded. I was thinking of this experience after I imported thousands of private keys:
This morning, Bitcoin Core was hanging. I killed it, restarted it, and it took forever to load the wallet (which had grown to 2.2 GB during the rescan). Eventually, it worked! It's up to date, and the total balance is 0 (as expected). Every few minutes, Bitcoin Core is unresponsive for a few minutes, most likely because of the large wallet combined with a lack of processing power. It's not very nice to work with, and consumes 1 full CPU core.
If I'd want to check a large number of addresses, I'd use this:
How to useThe most likely use is to check a long list of Bitcoin addresses for a remaining balance.
On Linux, use this to find matching addresses (after extrating the compressed .gz file of course):
comm -12 Bitcoin_addresses_LATEST.txt <(cat mylist.txt | sort | uniq)
- Bitcoin_addresses_LATEST.txt: the extracted latest version downloaded from addresses.loyce.club.
- mylist.txt: your own list of addresses, one address per line.
This takes only seconds to check millions of addresses.