[andydb]

You've run into a "rough edge" of the beta release that will be fixed soon. When you keep the Cluster Overview page open, it runs queries against your cluster so that it can display information like "# databases in the cluster". Unfortunately, those queries run every 10 seconds in the background, and are consuming RUs, which is why you see RU usage without having connected to the cluster yet. But never fear, we'll get that fixed.

One thing that may not be clear - you get 10M RUs for free, up front, but you also get a constant accumulation of 100 RU/s for free throughout the month. That adds up to >250M free RUs per month. This ensures that your cluster is always accessible, and that you never truly "run out" of RUs - at most you get throttled to 100 RU/s.

I hear you on the difficulty of understanding how your queries map to RUs. SQL queries can be enormously complex and differ by multiple orders of magnitude from one another in terms of their compute cost. That's why we built a near real-time dashboard that shows you how quickly you're consuming RUs. You can run your workload for a few minutes and then check back on the dashboard to see how many RUs that workload consumed.