docs: add a section about latency and how it's measured (#16734)

closes https://github.com/coder/coder/issues/14942

- what latency is measured
- where it's reported
- how users experience latency
- how to lower latency



[preview](https://coder.com/docs/@14942-latency/admin/networking#latency)

---------

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>

docs/admin/networking/index.md

@@ -197,6 +197,64 @@ low-latency browser experiences for geo-distributed teams.
 
 To learn more, see [Workspace Proxies](./workspace-proxies.md).
 
+## Latency
+
+Coder measures and reports several types of latency, providing insights into the performance of your deployment. Understanding these metrics can help you diagnose issues and optimize the user experience.
+
+There are three main types of latency metrics for your Coder deployment:
+
+- Dashboard-to-server latency:
+
+  The Coder UI measures round-trip time to the Coder server or workspace proxy using built-in browser timing capabilities.
+
+  This appears in the user interface next to your username, showing how responsive the dashboard is.
+
+- Workspace connection latency:
+
+  The latency shown on the workspace dashboard measures the round-trip time between the workspace agent and its DERP relay server.
+
+  This metric is displayed in milliseconds on the workspace dashboard and specifically shows the agent-to-relay latency, not direct P2P connections.
+
+  To estimate the total end-to-end latency experienced by a user, add the dashboard-to-server latency to this agent-to-relay latency.
+
+- Database latency:
+
+  For administrators, Coder monitors and reports database query performance in the health dashboard.
+
+### How latency is classified
+
+Latency measurements are color-coded in the dashboard:
+
+- **Green** (<150ms): Good performance.
+- **Yellow** (150-300ms): Moderate latency that might affect user experience.
+- **Red** (>300ms): High latency that will noticeably affect user experience.
+
+### View latency information
+
+- **Dashboard**: The global latency indicator appears in the top navigation bar.
+- **Workspace list**: Each workspace shows its connection latency.
+- **Health dashboard**: Administrators can view advanced metrics including database latency.
+- **CLI**: Use `coder ping <workspace>` to measure and analyze latency from the command line.
+
+### Factors that affect latency
+
+- **Geographic distance**: Physical distance between users, Coder server, and workspaces.
+- **Network connectivity**: Quality of internet connections and routing.
+- **Infrastructure**: Cloud provider regions and network optimization.
+- **P2P connectivity**: Whether direct connections can be established or relays are needed.
+
+### How to optimize latency
+
+To improve latency and user experience:
+
+- **Deploy workspace proxies**: Place [proxies](./workspace-proxies.md) in regions closer to users, connecting back to your single Coder server deployment.
+- **Use P2P connections**: Ensure network configurations permit direct connections.
+- **Strategic placement**: Deploy your Coder server in a region where most users work.
+- **Network configuration**: Optimize routing between users and workspaces.
+- **Check firewall rules**: Ensure they don't block necessary Coder connections.
+
+For help troubleshooting connection issues, including latency problems, refer to the [networking troubleshooting guide](./troubleshooting.md).
+
 ## Up next
 
 - Learn about [Port Forwarding](./port-forwarding.md)

docs/admin/networking/workspace-proxies.md

@@ -208,6 +208,15 @@ up to 60 seconds.
 
 ![Workspace proxy picker](../../images/admin/networking/workspace-proxies/ws-proxy-picker.png)
 
+## Multiple workspace proxies
+
+When multiple workspace proxies are deployed:
+
+- The browser measures latency to each available proxy independently.
+- Users can select their preferred proxy from the dashboard.
+- The system can automatically select the lowest-latency proxy.
+- The dashboard latency indicator shows latency to the currently selected proxy.
+
 ## Observability
 
 Coder workspace proxy exports metrics via the HTTP endpoint, which can be