Github: https://github.com/spesmilo/electrumx
Server performance article: https://sparrowwallet.com/docs/server-performance.html
eletrumx.conf settings:
DB_DIRECTORY = /home/username/electrumx_db
DAEMON_URL = rpcusername:rpcpassword@localhost
SERVICES = tcp://0.0.0.0:50001
COIN = Bitcoin
PEER_DISCOVERY = off
COST_SOFT_LIMIT = 0
COST_HARD_LIMIT = 0