⚡ perf: Short-Circuit Config Override Resolution for Empty Principals (#12549)

Skip the getApplicableConfigs DB query when buildPrincipals returns
an empty array, since there are no principals to match against.

packages/api/src/app/service.spec.ts

@@ -201,14 +201,16 @@ describe('createAppConfigService', () => {
       const deps = createDeps({ getApplicableConfigs: mockGetConfigs });
       const { getAppConfig } = createAppConfigService(deps);
 
+      // No role/userId → empty principals → short-circuits without calling getApplicableConfigs
       await getAppConfig();
+      expect(mockGetConfigs).not.toHaveBeenCalled();
 
       mockGetConfigs.mockResolvedValueOnce([
         { priority: 10, overrides: { restricted: true }, isActive: true },
       ]);
       const config = await getAppConfig({ role: 'ADMIN' });
 
-      expect(mockGetConfigs).toHaveBeenCalledTimes(2);
+      expect(mockGetConfigs).toHaveBeenCalledTimes(1);
       expect((config as TestConfig).restricted).toBe(true);
     });
 
@@ -229,6 +231,29 @@ describe('createAppConfigService', () => {
       expect((config as TestConfig).x).toBe('admin-only');
     });
 
+    it('skips getApplicableConfigs when buildPrincipals returns empty', async () => {
+      const deps = createDeps({
+        getUserPrincipals: jest.fn().mockResolvedValue([]),
+      });
+      const { getAppConfig } = createAppConfigService(deps);
+
+      const config = await getAppConfig({ userId: 'uid1', role: 'USER' });
+
+      expect(deps.getUserPrincipals).toHaveBeenCalledWith({ userId: 'uid1', role: 'USER' });
+      expect(deps.getApplicableConfigs).not.toHaveBeenCalled();
+      expect(config).toEqual(deps._baseConfig);
+    });
+
+    it('skips getApplicableConfigs when no role or userId is provided', async () => {
+      const deps = createDeps();
+      const { getAppConfig } = createAppConfigService(deps);
+
+      const config = await getAppConfig();
+
+      expect(deps.getApplicableConfigs).not.toHaveBeenCalled();
+      expect(config).toEqual(deps._baseConfig);
+    });
+
     it('falls back to base config on getApplicableConfigs error', async () => {
       const deps = createDeps({
         getApplicableConfigs: jest.fn().mockRejectedValue(new Error('DB down')),

packages/api/src/app/service.ts

@@ -170,6 +170,12 @@ export function createAppConfigService(deps: AppConfigServiceDeps) {
 
     try {
       const principals = await buildPrincipals(role, userId);
+
+      if (principals.length === 0) {
+        await cache.set(cacheKey, baseConfig, overrideCacheTtl);
+        return baseConfig;
+      }
+
       const configs = await getApplicableConfigs(principals);
 
       if (configs.length === 0) {