documentation for probes

Signed-off-by: Kavindu Dodanduwa <[email protected]>

docs/other_resources/high_level_architecture.md

@@ -26,4 +26,22 @@ flag configurations watched by the respective implementation. For example, the f
 The update provided by sync implementation is pushed to the evaluator engine, which interprets the event and forwards it to the state store. Change notifications generated in the 
 process gets pushed to event subscribers.
 
-<img src="../images/of-flagd-1.png" width="560">
+<img src="../images/of-flagd-1.png" width="560">
+
+## Readiness & Liveness probes
+
+Flagd exposes HTTP liveness and readiness probes. These probes can be used for K8s deployments. With default 
+start-up configurations, these probes are exposed at the following URLs,
+
+- Liveness: http://localhost:8014/healthz
+- Readiness: http://localhost:8014/readyz
+
+### Definition of Liveness
+
+The liveness probe becomes active and HTTP 200 status is served as soon as Flagd service is up and running.
+
+### Definition of Readiness
+
+The readiness probe becomes active similar to the liveness probe as soon as Flagd service is up and running. However,
+the probe emits HTTP 412 until all sync providers are ready. This status changes to HTTP 200 when all sync providers at
+least have one successful data sync. The status does not change from there on.