Cart performance
PHP-FPM, OPcache, Redis, Memcached and a fast database help serve catalog, search, cart and admin panel.
Not every shop view should be aggressively cached, so application-specific configuration matters.
Trust and e-mail
SSL, correct DNS, SPF, DKIM, DMARC and stable e-mail affect orders, notifications and customer communication.
SMTP delivery confirmations help verify whether the recipient server accepted a message.
Data protection
Account backups, malware scanners, Imunify360, CXS and data center procedures reduce the impact of failures or infections.
For shops, GDPR, access control and process documentation also matter.