Enhance README with persistence architecture details

Added information about multi-tier persistence architecture.

Author: tstromberg

README.md

@@ -8,7 +8,9 @@
 
 <img src="media/logo-small.png" alt="fido logo" width="200">
 
-fido is a high-performance cache for Go, focusing on high hit-rates, high throughput, and low latency. Optimized using the best algorithms and lock-free data structures, nobody fetches better than Fido. Designed to thrive in unstable environments like Kubernetes, Cloud Run, or Borg, it also features an optional multi-tier persistence architecture.
+fido is a high-performance cache for Go, focusing on high hit-rates, high throughput, and low latency. Optimized using the best algorithms and lock-free data structures, nobody fetches better than Fido. Designed to thrive in unstable environments like Kubernetes, Cloud Run, or Borg.
+
+It also features an optional multi-tier persistence architecture, so you can also think of it as an in-process redis/valkey replacement.
 
 As of January 2026, nobody fetches better - and we have the [benchmarks](https://github.com/tstromberg/gocachemark/blob/main/latest/gocachemark-results.pdf) to prove it.