Your DB Is Still Red After Adding a Cache — Here's Why (opens in new tab)

You deployed a cache in front of your database three weeks ago. The DB is still running at 90% utilization. Traffic doubled last month and you're wondering if the cache is doing anything at all. It is — just not as much as you expected, because cache hit rate is not something you configure. It emerges from two things: how much of your working set fits in memory, and how skewed your access patterns are. Paperstack is a free system design simulator that makes this visible. Sketch an architectur...