Prefer hooks over overrides: "I customise checkout with woocommerce_checkout_fields to add or modify fields and woocommerce_checkout_update_order_meta to save them. Template overrides are a last resort because they break on WooCommerce updates."
WooCommerce provides extensive hooks for every part of the purchase flow: woocommerce_before_cart, woocommerce_checkout_process, woocommerce_payment_complete, etc. Template overrides: copy WooCommerce template files to your theme under woocommerce/ directory. Checkout customisation: add fields with woocommerce_after_order_notes, validate with woocommerce_checkout_process, save with woocommerce_checkout_update_order_meta. For payment gateways: extend WC_Payment_Gateway. Strong candidates discuss: the risk of template overrides becoming stale on WooCommerce updates, using hooks instead of overrides where possible, the WooCommerce REST API for headless commerce, and HPOS (High-Performance Order Storage) compatibility.
Tests ecommerce WordPress skills. Candidates who modify WooCommerce core files or rely heavily on template overrides will create maintenance nightmares. Those who understand the hook-first approach and HPOS compatibility build future-proof stores.