WordPress interview questions

A child theme inherits the design and templates of a parent theme and holds only your changes. Updates to the parent then do not erase your work. For example, I would put a custom header template and extra CSS for a client in a child theme of the theme they bought.

I ask whether the feature should survive a theme change. Styling and layout go in the child theme, while things like a custom post type, a form handler or tracking code go in a small plugin. That way switching themes never silently removes a business feature.

First I check whether I can reach the admin area, then turn on debug logging to see the actual error. If a plugin caused it, I disable that plugin by renaming its folder, restore the site and then test the update on staging. If needed, I restore from the backup taken before the update.

Strong unique passwords with two-factor authentication for admins, roles kept to the minimum needed, and regular updates of core, themes and plugins. I remove unused plugins and themes, keep off-site backups and restrict access to wp-config.php. I also prefer a few well-maintained plugins over many small ones.

Automatic daily backups of the database and files stored away from the server, kept for several weeks. Before major updates I take a fresh backup, test on a staging copy and then update live at a quiet time. Every few months I do a test restore to prove the backups work.

I measure first, then look at the usual causes: oversized images, too many heavy plugins, no page caching and slow hosting. Typical fixes are compressing and resizing images, removing unused plugins, adding caching and checking that the database is not bloated. I re-measure after each change so I know what helped.