diff --git a/src/config/config.server.ts b/src/config/config.server.ts
index da33f553a3..5e8d8e1587 100644
--- a/src/config/config.server.ts
+++ b/src/config/config.server.ts
@@ -11,8 +11,6 @@ import { isNotEmpty } from '../app/shared/empty.util';
 
 const CONFIG_PATH = join(process.cwd(), 'config');
 
-const APP_CONFIG_PATH = join(CONFIG_PATH, 'appConfig.json');
-
 type Environment = 'production' | 'development' | 'test';
 
 const getBooleanFromString = (variable: string): boolean => {
@@ -47,7 +45,7 @@ const getEnvironment = (): Environment => {
 
 const getLocalConfigPath = (env: Environment) => {
   // default to config/appConfig.json
-  let localConfigPath = APP_CONFIG_PATH;
+  let localConfigPath = join(CONFIG_PATH, 'appConfig.json');
 
   // determine app config filename variations
   let envVariations;
@@ -65,9 +63,9 @@ const getLocalConfigPath = (env: Environment) => {
 
   // check if any environment variations of app config exist
   for (const envVariation of envVariations) {
-    const altDistConfigPath = join(CONFIG_PATH, `appConfig.${envVariation}.json`);
-    if (fs.existsSync(altDistConfigPath)) {
-      localConfigPath = altDistConfigPath;
+    const envLocalConfigPath = join(CONFIG_PATH, `appConfig.${envVariation}.json`);
+    if (fs.existsSync(envLocalConfigPath)) {
+      localConfigPath = envLocalConfigPath;
     }
   }
 
@@ -106,7 +104,6 @@ const overrideWithEnvironment = (config: Config, key: string = '') => {
             default:
               console.warn(`Unsupported environment variable type ${typeof innerConfig} ${variable}`);
           }
-          
         }
       }
     }
@@ -122,6 +119,16 @@ const buildBaseUrl = (config: ServerConfig): void => {
   ].join('');
 };
 
+/**
+ * Build app config with the following chain of override.
+ *
+ * local config -> environment local config -> external config -> environment variable
+ *
+ * Optionally save to file.
+ *
+ * @param destConfigPath optional path to save config file
+ * @returns app config
+ */
 export const buildAppConfig = (destConfigPath?: string): AppConfig => {
   // start with default app config
   const appConfig: AppConfig = new DefaultAppConfig();
@@ -141,11 +148,11 @@ export const buildAppConfig = (destConfigPath?: string): AppConfig => {
   }
 
   // override with dist config
-  const distConfigPath = getLocalConfigPath(env);
-  if (fs.existsSync(distConfigPath)) {
-    overrideWithConfig(appConfig, distConfigPath);
+  const localConfigPath = getLocalConfigPath(env);
+  if (fs.existsSync(localConfigPath)) {
+    overrideWithConfig(appConfig, localConfigPath);
   } else {
-    console.warn(`Unable to find dist config file at ${distConfigPath}`);
+    console.warn(`Unable to find dist config file at ${localConfigPath}`);
   }
 
   // override with external config if specified by environment variable `APP_CONFIG_PATH`
diff --git a/src/config/config.util.spec.ts b/src/config/config.util.spec.ts
index cb2fdcdba2..f9989f5a83 100644
--- a/src/config/config.util.spec.ts
+++ b/src/config/config.util.spec.ts
@@ -1,17 +1,56 @@
 import { environment } from '../environments/environment.prod';
 import { extendEnvironmentWithAppConfig } from './config.util';
 import { DefaultAppConfig } from './default-app-config';
+import { HandleThemeConfig } from './theme.model';
 
 describe('Config Util', () => {
   describe('extendEnvironmentWithAppConfig', () => {
     it('should extend prod environment with app config', () => {
       const appConfig = new DefaultAppConfig();
-      const originalMsToLive = appConfig.cache.msToLive.default;
-      expect(originalMsToLive).toEqual(15 * 60 * 1000); // 15 minute
+      expect(appConfig.cache.msToLive.default).toEqual(15 * 60 * 1000); // 15 minute
+      expect(appConfig.ui.rateLimiter.windowMs).toEqual(1 * 60 * 1000); // 1 minute
+      expect(appConfig.ui.rateLimiter.max).toEqual(500);
+
+      expect(appConfig.submission.autosave.metadata).toEqual([]);
+
+      expect(appConfig.themes.length).toEqual(1);
+      expect(appConfig.themes[0].name).toEqual('dspace');
+
       const msToLive = 1 * 60 * 1000; // 1 minute
       appConfig.cache.msToLive.default = msToLive;
+
+      const rateLimiter = {
+        windowMs: 5 * 50 * 1000, // 5 minutes
+        max: 1000
+      };
+      appConfig.ui.rateLimiter = rateLimiter;
+
+      const autoSaveMetadata = [
+        'dc.author',
+        'dc.title'
+      ];
+
+      appConfig.submission.autosave.metadata = autoSaveMetadata;
+
+      const customTheme: HandleThemeConfig = {
+        name: 'custom',
+        handle: '10673/1233'
+      };
+
+      appConfig.themes.push(customTheme);
+
       extendEnvironmentWithAppConfig(environment, appConfig);
+
       expect(environment.cache.msToLive.default).toEqual(msToLive);
+      expect(environment.ui.rateLimiter.windowMs).toEqual(rateLimiter.windowMs);
+      expect(environment.ui.rateLimiter.max).toEqual(rateLimiter.max);
+      expect(environment.submission.autosave.metadata[0]).toEqual(autoSaveMetadata[0]);
+      expect(environment.submission.autosave.metadata[1]).toEqual(autoSaveMetadata[1]);
+
+      expect(environment.themes.length).toEqual(2);
+      expect(environment.themes[0].name).toEqual('dspace');
+      expect(environment.themes[1].name).toEqual(customTheme.name);
+      expect((environment.themes[1] as HandleThemeConfig).handle).toEqual(customTheme.handle);
     });
   });
 });
diff --git a/src/config/config.util.ts b/src/config/config.util.ts
index 9f2d7d349e..6c3b9e0f7a 100644
--- a/src/config/config.util.ts
+++ b/src/config/config.util.ts
@@ -7,21 +7,38 @@ import { hasNoValue } from '../app/shared/empty.util';
 import { AppConfig } from './app-config.interface';
 import { ThemeConfig } from './theme.model';
 
+/**
+ * Extend Angular environment with app config.
+ *
+ * @param env       environment object
+ * @param appConfig app config
+ */
 const extendEnvironmentWithAppConfig = (env: any, appConfig: AppConfig): void => {
   mergeConfig(env, appConfig);
   console.log(`Environment extended with app config`);
 };
 
-const mergeConfig = (config: any, appConfig: AppConfig): void => {
+/**
+ * Merge one config into another.
+ *
+ * @param destinationConfig destination config
+ * @param sourceConfig      source config
+ */
+const mergeConfig = (destinationConfig: any, sourceConfig: AppConfig): void => {
   const mergeOptions = {
     arrayMerge: (destinationArray, sourceArray, options) => sourceArray
   };
-  Object.assign(config, merge.all([
-    config,
-    appConfig
+  Object.assign(destinationConfig, merge.all([
+    destinationConfig,
+    sourceConfig
   ], mergeOptions));
 };
 
+/**
+ * Get default them config from environment.
+ *
+ * @returns default theme config
+ */
 const getDefaultThemeConfig = (): ThemeConfig => {
   return environment.themes.find((themeConfig: any) =>
     hasNoValue(themeConfig.regex) &&