diff --git a/CHANGELOG.md b/CHANGELOG.md
index 51e3eb1..42463cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,13 @@
+## 0.5
+- Added `Currency`
+- Added `Restrr#retrieveAllCurrencies`
+- Added `Restrr#createCurrency`
+- Added `Restrr#retrieveCurrencyById`
+- Added `Restrr#deleteCurrencyById`
+- Added `Restrr#updateCurrencyById`
+- Added `Restrr#retrieveSelf`
+- Implemented (Batch)CacheViews (some retrieve methods now have a `forceRetrieve` parameter)
+
 ## 0.4.2
 - Fixed missing `isWeb` in `RestrrBuilder#create`
 
diff --git a/lib/restrr.dart b/lib/restrr.dart
index 9ef135c..6f56c48 100644
--- a/lib/restrr.dart
+++ b/lib/restrr.dart
@@ -5,6 +5,7 @@ export 'src/entity_builder.dart';
 export 'src/restrr_base.dart';
 
 /* [ /src/entities ] */
+export 'src/entities/currency.dart';
 export 'src/entities/health_response.dart';
 export 'src/entities/restrr_entity.dart';
 export 'src/entities/user.dart';
diff --git a/lib/src/cache/batch_cache_view.dart b/lib/src/cache/batch_cache_view.dart
new file mode 100644
index 0000000..f93e4c4
--- /dev/null
+++ b/lib/src/cache/batch_cache_view.dart
@@ -0,0 +1,13 @@
+import '../../restrr.dart';
+
+class RestrrEntityBatchCacheView<T extends RestrrEntity> {
+  List<T>? _lastSnapshot;
+
+  List<T>? get() => _lastSnapshot;
+
+  void update(List<T> value) => _lastSnapshot = value;
+
+  void clear() => _lastSnapshot = null;
+
+  bool get hasSnapshot => _lastSnapshot != null;
+}
\ No newline at end of file
diff --git a/lib/src/cache/cache_view.dart b/lib/src/cache/cache_view.dart
new file mode 100644
index 0000000..c2d7efb
--- /dev/null
+++ b/lib/src/cache/cache_view.dart
@@ -0,0 +1,15 @@
+import 'package:restrr/restrr.dart';
+
+class RestrrEntityCacheView<T extends RestrrEntity> {
+  final Map<ID, T> _cache = {};
+
+  T? get(ID id) => _cache[id];
+
+  T cache(T value) => _cache[value.id] = value;
+
+  T? remove(ID id) => _cache.remove(id);
+
+  void clear() => _cache.clear();
+
+  bool contains(ID id) => _cache.containsKey(id);
+}
diff --git a/lib/src/entities/currency.dart b/lib/src/entities/currency.dart
new file mode 100644
index 0000000..89c9d5d
--- /dev/null
+++ b/lib/src/entities/currency.dart
@@ -0,0 +1,42 @@
+import 'package:restrr/restrr.dart';
+
+abstract class Currency implements RestrrEntity {
+  String get name;
+  String get symbol;
+  String get isoCode;
+  int get decimalPlaces;
+  int? get user;
+
+  bool get isCustom;
+
+  bool isCreatedBy(User user);
+}
+
+class CurrencyImpl extends RestrrEntityImpl implements Currency {
+  @override
+  final String name;
+  @override
+  final String symbol;
+  @override
+  final String isoCode;
+  @override
+  final int decimalPlaces;
+  @override
+  final int? user;
+
+  const CurrencyImpl({
+    required super.api,
+    required super.id,
+    required this.name,
+    required this.symbol,
+    required this.isoCode,
+    required this.decimalPlaces,
+    required this.user,
+  });
+
+  @override
+  bool get isCustom => user != null;
+
+  @override
+  bool isCreatedBy(User user) => this.user == user.id;
+}
diff --git a/lib/src/entities/restrr_entity.dart b/lib/src/entities/restrr_entity.dart
index f568523..caeda28 100644
--- a/lib/src/entities/restrr_entity.dart
+++ b/lib/src/entities/restrr_entity.dart
@@ -1,17 +1,24 @@
 import '../../restrr.dart';
 
+typedef ID = int;
+
 /// The base class for all Restrr entities.
 /// This simply provides a reference to the Restrr instance.
 abstract class RestrrEntity {
   /// A reference to the Restrr instance.
   Restrr get api;
+
+  ID get id;
 }
 
 class RestrrEntityImpl implements RestrrEntity {
   @override
   final Restrr api;
+  @override
+  final ID id;
 
   const RestrrEntityImpl({
     required this.api,
+    required this.id,
   });
 }
diff --git a/lib/src/entities/user.dart b/lib/src/entities/user.dart
index 6aae6f1..8937aad 100644
--- a/lib/src/entities/user.dart
+++ b/lib/src/entities/user.dart
@@ -1,7 +1,6 @@
 import '../../restrr.dart';
 
 abstract class User extends RestrrEntity {
-  int get id;
   String get username;
   String? get email;
   String? get displayName;
@@ -14,8 +13,6 @@ abstract class User extends RestrrEntity {
 }
 
 class UserImpl extends RestrrEntityImpl implements User {
-  @override
-  final int id;
   @override
   final String username;
   @override
@@ -29,7 +26,7 @@ class UserImpl extends RestrrEntityImpl implements User {
 
   const UserImpl({
     required super.api,
-    required this.id,
+    required super.id,
     required this.username,
     required this.email,
     required this.displayName,
diff --git a/lib/src/entity_builder.dart b/lib/src/entity_builder.dart
index f5df14c..275adb5 100644
--- a/lib/src/entity_builder.dart
+++ b/lib/src/entity_builder.dart
@@ -15,7 +15,7 @@ class EntityBuilder {
   }
 
   User buildUser(Map<String, dynamic> json) {
-    return UserImpl(
+    final UserImpl user = UserImpl(
       api: api,
       id: json['id'],
       username: json['username'],
@@ -24,5 +24,19 @@ class EntityBuilder {
       createdAt: DateTime.parse(json['created_at']),
       isAdmin: json['is_admin'],
     );
+    return api.userCache.cache(user);
+  }
+
+  Currency buildCurrency(Map<String, dynamic> json) {
+    final CurrencyImpl currency = CurrencyImpl(
+      api: api,
+      id: json['id'],
+      name: json['name'],
+      symbol: json['symbol'],
+      isoCode: json['iso_code'],
+      decimalPlaces: json['decimal_places'],
+      user: json['user'],
+    );
+    return api.currencyCache.cache(currency);
   }
 }
diff --git a/lib/src/requests/route.dart b/lib/src/requests/route.dart
index c35a14d..93cd8ed 100644
--- a/lib/src/requests/route.dart
+++ b/lib/src/requests/route.dart
@@ -37,18 +37,18 @@ class Route {
 
   Route.patch(String path, {bool isVersioned = true}) : this._('PATCH', path, isVersioned: isVersioned);
 
-  CompiledRoute compile({List<String> params = const []}) {
+  CompiledRoute compile({List<dynamic> params = const []}) {
     if (params.length != paramCount) {
       throw ArgumentError(
           'Error compiling route [$method $path}]: Incorrect amount of parameters! Expected: $paramCount, Provided: ${params.length}');
     }
     final Map<String, String> values = {};
     String compiledRoute = path;
-    for (String param in params) {
+    for (dynamic param in params) {
       int paramStart = compiledRoute.indexOf('{');
       int paramEnd = compiledRoute.indexOf('}');
-      values[compiledRoute.substring(paramStart + 1, paramEnd)] = param;
-      compiledRoute = compiledRoute.replaceRange(paramStart, paramEnd + 1, param);
+      values[compiledRoute.substring(paramStart + 1, paramEnd)] = param.toString();
+      compiledRoute = compiledRoute.replaceRange(paramStart, paramEnd + 1, param.toString());
     }
     return CompiledRoute(this, compiledRoute, values);
   }
diff --git a/lib/src/requests/route_definitions.dart b/lib/src/requests/route_definitions.dart
index 9057b4d..4a0b4eb 100644
--- a/lib/src/requests/route_definitions.dart
+++ b/lib/src/requests/route_definitions.dart
@@ -15,3 +15,13 @@ class UserRoutes {
   static final Route logout = Route.delete('/user/logout');
   static final Route register = Route.post('/user/register');
 }
+
+class CurrencyRoutes {
+  const CurrencyRoutes._();
+
+  static final Route retrieveAll = Route.get('/currency');
+  static final Route create = Route.post('/currency/{currencyId}');
+  static final Route retrieveById = Route.get('/currency/{currencyId}');
+  static final Route deleteById = Route.delete('/currency/{currencyId}');
+  static final Route updateById = Route.patch('/currency/{currencyId}');
+}
diff --git a/lib/src/restrr_base.dart b/lib/src/restrr_base.dart
index abb4192..a44cf83 100644
--- a/lib/src/restrr_base.dart
+++ b/lib/src/restrr_base.dart
@@ -1,9 +1,12 @@
 import 'package:logging/logging.dart';
+import 'package:restrr/src/cache/batch_cache_view.dart';
 import 'package:restrr/src/requests/route.dart';
 import 'package:restrr/src/service/api_service.dart';
+import 'package:restrr/src/service/currency_service.dart';
 import 'package:restrr/src/service/user_service.dart';
 
 import '../restrr.dart';
+import 'cache/cache_view.dart';
 
 class RestrrOptions {
   final bool isWeb;
@@ -59,7 +62,7 @@ class RestrrBuilder {
 
   /// Logs in with the given [username] and [password].
   Future<RestResponse<RestrrImpl>> _handleLogin(RestrrImpl apiImpl, String username, String password) async {
-    final RestResponse<User> response = await apiImpl.userService.login(username, password);
+    final RestResponse<User> response = await apiImpl._userService.login(username, password);
     if (!response.hasData) {
       Restrr.log.warning('Invalid credentials for user $username');
       return RestrrError.invalidCredentials.toRestResponse(statusCode: response.statusCode);
@@ -73,7 +76,7 @@ class RestrrBuilder {
   Future<RestResponse<RestrrImpl>> _handleRegistration(RestrrImpl apiImpl, String username, String password,
       {String? email, String? displayName}) async {
     final RestResponse<User> response =
-        await apiImpl.userService.register(username, password, email: email, displayName: displayName);
+        await apiImpl._userService.register(username, password, email: email, displayName: displayName);
     if (response.hasError) {
       Restrr.log.warning('Failed to register user $username');
       return response.error?.toRestResponse(statusCode: response.statusCode) ?? RestrrError.unknown.toRestResponse();
@@ -85,7 +88,7 @@ class RestrrBuilder {
 
   /// Attempts to refresh the session with still saved credentials.
   Future<RestResponse<RestrrImpl>> _handleSavedSession(RestrrImpl apiImpl) async {
-    final RestResponse<User> response = await apiImpl.userService.getSelf();
+    final RestResponse<User> response = await apiImpl._userService.getSelf();
     if (response.hasError) {
       Restrr.log.warning('Failed to refresh session');
       return response.error?.toRestResponse(statusCode: response.statusCode) ?? RestrrError.unknown.toRestResponse();
@@ -108,8 +111,6 @@ abstract class Restrr {
   /// The currently authenticated user.
   User get selfUser;
 
-  Future<bool> logout();
-
   /// Checks whether the given [uri] is valid and the API is healthy.
   static Future<RestResponse<HealthResponse>> checkUri(Uri uri, {bool isWeb = false}) async {
     return RequestHandler.request(
@@ -118,6 +119,23 @@ abstract class Restrr {
         isWeb: isWeb,
         routeOptions: RouteOptions(hostUri: uri));
   }
+
+  /// Retrieves the currently authenticated user.
+  Future<User?> retrieveSelf({bool forceRetrieve = false});
+
+  /// Logs out the current user.
+  Future<bool> logout();
+
+  Future<List<Currency>?> retrieveAllCurrencies({bool forceRetrieve = false});
+
+  Future<Currency?> createCurrency(
+      {required String name, required String symbol, required String isoCode, required int decimalPlaces});
+
+  Future<Currency?> retrieveCurrencyById(ID id, {bool forceRetrieve = false});
+
+  Future<bool> deleteCurrencyById(ID id);
+
+  Future<Currency?> updateCurrencyById(ID id, {String? name, String? symbol, String? isoCode, int? decimalPlaces});
 }
 
 class RestrrImpl implements Restrr {
@@ -126,7 +144,17 @@ class RestrrImpl implements Restrr {
   @override
   final RouteOptions routeOptions;
 
-  late final UserService userService = UserService(api: this);
+  /* Services */
+
+  late final UserService _userService = UserService(api: this);
+  late final CurrencyService _currencyService = CurrencyService(api: this);
+
+  /* Caches */
+
+  late final RestrrEntityCacheView<User> userCache = RestrrEntityCacheView();
+  late final RestrrEntityCacheView<Currency> currencyCache = RestrrEntityCacheView();
+
+  late final RestrrEntityBatchCacheView<Currency> _currencyBatchCache = RestrrEntityBatchCacheView();
 
   RestrrImpl._({required this.options, required this.routeOptions});
 
@@ -136,13 +164,89 @@ class RestrrImpl implements Restrr {
   @override
   late final User selfUser;
 
+  @override
+  Future<User?> retrieveSelf({bool forceRetrieve = false}) async {
+    return _getOrRetrieveSingle(
+        key: selfUser.id,
+        cacheView: userCache,
+        retrieveFunction: (api) => api._userService.getSelf(),
+        forceRetrieve: forceRetrieve);
+  }
+
   @override
   Future<bool> logout() async {
-    final RestResponse<bool> response = await UserService(api: this).logout();
+    final RestResponse<bool> response = await _userService.logout();
     if (response.hasData && response.data! && !options.isWeb) {
       await CompiledRoute.cookieJar.deleteAll();
       return true;
     }
     return false;
   }
+
+  @override
+  Future<List<Currency>?> retrieveAllCurrencies({bool forceRetrieve = false}) async {
+    return _getOrRetrieveMulti(
+        batchCache: _currencyBatchCache,
+        retrieveFunction: (api) => api._currencyService.retrieveAllCurrencies(),
+    );
+  }
+
+  @override
+  Future<Currency?> createCurrency(
+      {required String name, required String symbol, required String isoCode, required int decimalPlaces}) async {
+    final RestResponse<Currency> response = await _currencyService.createCurrency(
+        name: name, symbol: symbol, isoCode: isoCode, decimalPlaces: decimalPlaces);
+    return response.data;
+  }
+
+  @override
+  Future<Currency?> retrieveCurrencyById(ID id, {bool forceRetrieve = false}) async {
+    return _getOrRetrieveSingle(
+        key: id,
+        cacheView: currencyCache,
+        retrieveFunction: (api) => api._currencyService.retrieveCurrencyById(id),
+        forceRetrieve: forceRetrieve);
+  }
+
+  @override
+  Future<bool> deleteCurrencyById(ID id) async {
+    final RestResponse<bool> response = await _currencyService.deleteCurrencyById(id);
+    return response.hasData && response.data!;
+  }
+
+  @override
+  Future<Currency?> updateCurrencyById(ID id,
+      {String? name, String? symbol, String? isoCode, int? decimalPlaces}) async {
+    final RestResponse<Currency> response = await _currencyService.updateCurrencyById(id,
+        name: name, symbol: symbol, isoCode: isoCode, decimalPlaces: decimalPlaces);
+    return response.data;
+  }
+
+  Future<T?> _getOrRetrieveSingle<T extends RestrrEntity>(
+      {required ID key,
+      required RestrrEntityCacheView<T> cacheView,
+      required Future<RestResponse<T>> Function(RestrrImpl) retrieveFunction,
+      bool forceRetrieve = false}) async {
+    if (!forceRetrieve && cacheView.contains(key)) {
+      return cacheView.get(key)!;
+    }
+    final RestResponse<T> response = await retrieveFunction.call(this);
+    return response.hasData ? response.data : null;
+  }
+
+  Future<List<T>?> _getOrRetrieveMulti<T extends RestrrEntity>(
+      {required RestrrEntityBatchCacheView<T> batchCache,
+      required Future<RestResponse<List<T>>> Function(RestrrImpl) retrieveFunction,
+      bool forceRetrieve = false}) async {
+    if (!forceRetrieve && batchCache.hasSnapshot) {
+      return batchCache.get()!;
+    }
+    final RestResponse<List<T>> response = await retrieveFunction.call(this);
+    if (response.hasData) {
+      final List<T> remote = response.data!;
+      batchCache.update(remote);
+      return remote;
+    }
+    return null;
+  }
 }
diff --git a/lib/src/service/currency_service.dart b/lib/src/service/currency_service.dart
new file mode 100644
index 0000000..a89626b
--- /dev/null
+++ b/lib/src/service/currency_service.dart
@@ -0,0 +1,69 @@
+import 'package:restrr/restrr.dart';
+
+import 'api_service.dart';
+
+class CurrencyService extends ApiService {
+  const CurrencyService({required super.api});
+
+  Future<RestResponse<List<Currency>>> retrieveAllCurrencies() async {
+    return multiRequest(
+        route: CurrencyRoutes.retrieveAll.compile(),
+        mapper: (json) => api.entityBuilder.buildCurrency(json),
+        errorMap: {
+          401: RestrrError.notSignedIn,
+        });
+  }
+
+  Future<RestResponse<Currency>> createCurrency(
+      {required String name, required String symbol, required String isoCode, required int decimalPlaces}) async {
+    return request(
+        route: CurrencyRoutes.create.compile(),
+        mapper: (json) => api.entityBuilder.buildCurrency(json),
+        body: {
+          'name': name,
+          'symbol': symbol,
+          'iso_code': isoCode,
+          'decimal_places': decimalPlaces,
+        },
+        errorMap: {
+          401: RestrrError.notSignedIn,
+        });
+  }
+
+  Future<RestResponse<Currency>> retrieveCurrencyById(ID id) async {
+    return request(
+        route: CurrencyRoutes.retrieveById.compile(params: [id]),
+        mapper: (json) => api.entityBuilder.buildCurrency(json),
+        errorMap: {
+          401: RestrrError.notSignedIn,
+          404: RestrrError.notFound,
+        });
+  }
+
+  Future<RestResponse<bool>> deleteCurrencyById(ID id) async {
+    return noResponseRequest(route: CurrencyRoutes.deleteById.compile(params: [id]), errorMap: {
+      401: RestrrError.notSignedIn,
+      404: RestrrError.notFound,
+    });
+  }
+
+  Future<RestResponse<Currency>> updateCurrencyById(ID id,
+      {String? name, String? symbol, String? isoCode, int? decimalPlaces}) async {
+    if (name == null && symbol == null && isoCode == null && decimalPlaces == null) {
+      throw ArgumentError('At least one field must be set');
+    }
+    return request(
+        route: CurrencyRoutes.updateById.compile(params: [id]),
+        mapper: (json) => api.entityBuilder.buildCurrency(json),
+        body: {
+          if (name != null) 'name': name,
+          if (symbol != null) 'symbol': symbol,
+          if (isoCode != null) 'iso_code': isoCode,
+          if (decimalPlaces != null) 'decimal_places': decimalPlaces,
+        },
+        errorMap: {
+          401: RestrrError.notSignedIn,
+          404: RestrrError.notFound,
+        });
+  }
+}
diff --git a/pubspec.yaml b/pubspec.yaml
index e1652bc..401ab90 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: restrr
 description: Dart package which allows to communicate with the financrr REST API.
-version: 0.4.2
+version: 0.5.0
 repository: https://github.com/financrr/restrr
 
 environment:
diff --git a/test/restrr_entity_test.dart b/test/restrr_entity_test.dart
index ed4f353..5a5c47f 100644
--- a/test/restrr_entity_test.dart
+++ b/test/restrr_entity_test.dart
@@ -24,6 +24,17 @@ const String userJson = '''
 }
 ''';
 
+const String currencyJson = '''
+{
+  "id": 1,
+  "name": "US Dollar",
+  "symbol": "\$",
+  "iso_code": "USD",
+  "decimal_places": 2,
+  "user": 1
+}
+''';
+
 void main() {
   late Restrr api;
 
@@ -40,7 +51,7 @@ void main() {
       expect(healthResponse.details, null);
     });
 
-    test('.buildUser', () {
+    test('.buildUser', () async {
       final User user = api.entityBuilder.buildUser(jsonDecode(userJson));
       expect(user.id, 1);
       expect(user.username, 'admin');
@@ -48,5 +59,15 @@ void main() {
       expect(user.createdAt, DateTime.parse('+002024-02-17T20:48:43.391176000Z'));
       expect(user.isAdmin, true);
     });
+
+    test('.buildCurrency', () {
+      final Currency currency = api.entityBuilder.buildCurrency(jsonDecode(currencyJson));
+      expect(currency.id, 1);
+      expect(currency.name, 'US Dollar');
+      expect(currency.symbol, '\$');
+      expect(currency.isoCode, 'USD');
+      expect(currency.decimalPlaces, 2);
+      expect(currency.user, 1);
+    });
   });
 }