Add in-memory read cache with CUD-based invalidation

backend/app/api/me.py

@@ -9,6 +9,7 @@ from app.schemas.auth import ProviderPrincipal, MeSummaryResponse
 from app.schemas.permissions import RoleSnapshotResponse
 from app.security.idp_jwt import require_authenticated_principal
 from app.services.permission_service import PermissionService
+from app.services.runtime_cache import runtime_cache
 
 router = APIRouter(prefix="/me", tags=["me"])
 
@@ -18,6 +19,10 @@ def get_me(
     principal: ProviderPrincipal = Depends(require_authenticated_principal),
     db: Session = Depends(get_db),
 ) -> MeSummaryResponse:
+    cache_key = f"me:{principal.sub}"
+    cached = runtime_cache.get(cache_key)
+    if isinstance(cached, MeSummaryResponse):
+        return cached
     try:
         users_repo = UsersRepository(db)
         user = users_repo.upsert_by_sub(
@@ -28,13 +33,17 @@ def get_me(
             is_active=True,
             status="active",
         )
-        return MeSummaryResponse(sub=user.user_sub, email=user.email, display_name=user.display_name)
+        result = MeSummaryResponse(sub=user.user_sub, email=user.email, display_name=user.display_name)
+        runtime_cache.set(cache_key, result, ttl_seconds=30)
+        return result
     except SQLAlchemyError:
-        return MeSummaryResponse(
+        result = MeSummaryResponse(
             sub=principal.sub,
             email=principal.email,
             display_name=principal.name or principal.preferred_username,
         )
+        runtime_cache.set(cache_key, result, ttl_seconds=15)
+        return result
 
 
 @router.get("/permissions/snapshot", response_model=RoleSnapshotResponse)
@@ -42,6 +51,10 @@ def get_my_permission_snapshot(
     principal: ProviderPrincipal = Depends(require_authenticated_principal),
     db: Session = Depends(get_db),
 ) -> RoleSnapshotResponse:
+    cache_key = f"me:permissions_snapshot:{principal.sub}"
+    cached = runtime_cache.get(cache_key)
+    if isinstance(cached, RoleSnapshotResponse):
+        return cached
     try:
         users_repo = UsersRepository(db)
         user_sites_repo = UserSitesRepository(db)
@@ -68,6 +81,10 @@ def get_my_permission_snapshot(
             )
             for site, company, role, system in rows
         ]
-        return PermissionService.build_role_snapshot(user_sub=principal.sub, rows=serialized)
+        result = PermissionService.build_role_snapshot(user_sub=principal.sub, rows=serialized)
+        runtime_cache.set(cache_key, result, ttl_seconds=30)
+        return result
     except SQLAlchemyError:
-        return RoleSnapshotResponse(user_sub=principal.sub, roles=[])
+        result = RoleSnapshotResponse(user_sub=principal.sub, roles=[])
+        runtime_cache.set(cache_key, result, ttl_seconds=10)
+        return result