docs: Add Why and When for replication and update README features

README.md

@@ -44,6 +44,7 @@ phone-home, no hosted control plane, and no per-user pricing.
   drive the management API from scripts or CI, scoped to their own permissions.
 - **All-in-one Docker image** — app + OpenLDAP + Redis in one container, or run
   the pieces separately against your own LDAP/Redis via `app_*` env config.
+- **Multi-Site Support (Geo-Location Scaling)** — built-in support for N-Way Multi-Master OpenLDAP replication across physical sites for HA and low latency.
 
 ## Why this over the alternatives
 

docs/replication.md

@@ -7,6 +7,11 @@ title: Geo-Location Scaling (Replication)
 
 SSO Manager is built to be a self-contained identity provider, but if you have multiple physical sites, you may want a local copy of the directory at each site to ensure low latency and high availability.
 
+## Why and when to use this?
+- **High Availability (HA)**: If your primary site goes completely offline, your other sites can still authenticate users locally without depending on a WAN link.
+- **Low Latency**: Applications at a remote site can bind directly to their local LDAP server (`localhost` or LAN IP) instead of traversing the internet to query the primary site, making logins blazing fast.
+- **Independent Failure Domains**: By replicating only the LDAP directory (the source of truth) and keeping session state (Redis) independent, you prevent complex "split-brain" scenarios in the web UI. A failure at Site A won't bring down Site B.
+
 By default, the `sso-manager` Docker container runs a single, independent OpenLDAP instance. However, you can enable **N-Way Multi-Master Replication** via environment variables.
 
 ## How it works