Bounce rates are a nightmare if you don't get ahead of them. Found the biggest improvement from validating as early as possible - run a bulk clean nightly on the list, then plug an API into the sign-up form to catch syntax errors, disposable domains and obvious typos before they ever hit the database. Keep a close eye on the hard-bounce metric, if it stays high, a full list refresh is needed rather than just real-time checks. In my workflow, a bulk validator handles the nightly job and a lightweight API takes care of front-end validation - keeps latency low and costs predictable. If per-email pricing grates on you, a few services now offer flat-rate unlimited plans. Been testing ValiDora and it's been solid for both bulk and real-time validation without the headache.