ActiveRecord callbacks for lifecycle hooks

Callbacks hook into the ActiveRecord lifecycle to execute code before or after operations like create, update, or destroy. I use before_validation to normalize data (like downcasing emails), after_create to trigger welcome emails, and before_destroy to clean up associated resources. The key discipline is keeping callbacks focused on model-level concerns rather than business logic—complex workflows belong in service objects. I avoid callbacks that trigger external API calls or send emails directly, instead enqueueing background jobs. Callbacks can make debugging difficult when they're overused, so I prefer explicit service objects for orchestration and reserve callbacks for truly universal model behaviors. I also use prepend: true when callback order matters.