Why your shipping rates arrive attached to the wrong classes
Shipping classes are referenced by internal ID, and those IDs differ on every install. Copying the configuration between sites quietly scrambles it.
Notes
Field notes on WordPress performance, security and the parts of a build that usually go wrong.
The migration checklist that survives contact with a live site
Rehearse it, verify serialised data, map every redirect, and lower your TTL before you need to. Most migration disasters are one skipped step.
The SSL certificate went on and the site got slower
Enabling HTTPS should cost you a few milliseconds. When it costs seconds, the certificate is rarely the culprit on its own.