Hi! CEO of ReadySet here. You can think of ReadySet as being a cross between a traditional read replica and a custom caching layer (e.g. one you might build on top of Redis). With read replicas, you still rerun queries from scratch every time they're issued, which means you still have to think about things like query optimization. ReadySet caches frequently run queries in memory so you get super-fast query latencies on cache hits. Because of this, you can scale to much higher read throughputs without extra effort. This is especially useful for read-heavy applications (e.g. websites, certain types of dashboards, among others!)
You can read more about how it works here: https://docs.readyset.io/concepts/overview