Tell one. Have you ever done end-to-end performance testing?

In a recent project, I designed an end‑to‑end performance test for an e‑commerce platform. The test simulated 3,000 concurrent users performing the full purchase flow: browsing catalog, adding items to cart, checking out, and receiving confirmation emails. We used JMeter to script the UI and API interactions, and monitored the database, message queue, and CDN. The test ran for 8 hours to assess endurance. Results revealed a 30% slowdown in the payment service during peak hours, leading to a scaling recommendation that reduced latency by 40% after implementation.