A sale that goes well is a load test you cannot postpone. The weeks before it are much cheaper than the hours during it.
Test before you announce
Run load tests against realistic behaviour: browsing, searching, adding to cart and checking out, not just hitting the home page. Include the pages your campaign will send people to.
Cache what can be cached
- Serve category and product pages from cache wherever prices and stock allow it.
- Combine and minify static resources so each page needs fewer requests.
- Check that search indexes are current before traffic arrives.
Watch the whole path
Monitor page load time, checkout completion and error rates together. A fast home page and a slow payment step still lose sales. Agree in advance who watches the dashboards and what triggers a rollback.
After the rush
Review abandoned carts, the slowest pages and support tickets while they are fresh, then turn what you learned into next year’s checklist.