docs: A-2 — losing the database takes every node down while up stays 1

Both pods go NotReady, the Service endpoint list empties and the front door returns 503, so adding Keycloak replicas buys nothing against database loss. The node holding the session in cache fails too, because a refresh writes LAST_SESSION_REFRESH. Recovery was automatic in about fifteen seconds with no restart, which is what readiness rather than liveness buys.

The observability finding matters as much: up stayed at 1 through a total outage, so alerting on it would have caught nothing. kube-state-metrics is missing and pod readiness is therefore not recorded as a metric.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/evidence/a2-database-loss/03-four-paths.txt

@@ -0,0 +1,16 @@
+=== [1] 토큰을 새로 발급 (access 수명 60초) ===
+  발급 완료 sid=RKXQGAgkuLtouFMVPTFmp_0_
+
+=== [2] PostgreSQL 정지 ===
+  정지 시각: 11:56:04
+deployment.apps/postgres scaled
+pod/postgres-7b474b88c8-sn9ff condition met
+  삭제 완료: 11:56:04
+
+=== [3] 네 경로를 즉시 시험 ===
+  ④ 이미 발급된 access token 으로 관리 API   HTTP 000000{"error":"HTTP 401 Unauthorized"}401
+  ① 캐시를 가진 노드(keycloak-0)에서 refresh  HTTP 500
+  ② 캐시가 없는 노드(keycloak-1)에서 refresh  HTTP 500
+  ③ 새 로그인                                 HTTP 500
+  --- 오류 본문 (새 로그인) ---
+{"error":"unknown_error","error_description":"For more on this error consult the server log."}