diff --git a/docs/src/08_concepts.adoc b/docs/src/08_concepts.adoc
index b307352a..2aec4db4 100644
--- a/docs/src/08_concepts.adoc
+++ b/docs/src/08_concepts.adoc
@@ -213,44 +213,6 @@ class RestApiServiceImpl {
     + getQuestions(params: Map<String, String>): List<Question>
 }
 
-interface CrudRepository {
-    + save(entity: T): T
-    + findById(id: ID): Optional<T>
-    + findAll(): List<T>
-}
-
-interface PlayerRepository {
-    + findByEmail(email: String): Player
-    + findByUsername(nickname: String): Player
-}
-
-interface RoleRepository {
-}
-
-interface AnswerRepository {
-    + findByQuestion(question: Question): List<Answer>
-}
-
-interface ApiKeyRepository {
-    + findByKeyToken(key: String): ApiKey
-}
-
-interface CategoryRepository {
-    + findByName(name: String): Category
-}
-
-interface GameSessionRepository {
-}
-
-interface QuestionRepository {
-    + findByStatement(statement: String): Question
-}
-
-interface RestApiLogRepository {
-    + findByApiKey(apiKey: ApiKey): List<RestApiAccessLog>
-    + findByUser(user: Player): List<RestApiAccessLog>
-}
-
 class PlayerDto {
     - username: String
     - email: String
@@ -318,29 +280,6 @@ class QuestionGeneratorTestController {
     + test(): void
 }
 
-class HomeController {
-    - playerService: PlayerService
-    + home(): String
-    + apiHome(): String
-}
-
-class PlayersController {
-    - playerService: PlayerService
-    - signUpValidator: SignUpValidator
-    + showRegistrationForm(model: Model): String
-    + registerUserAccount(request: HttpServletRequest, user: PlayerDto, result: BindingResult, model: Model): String
-    + showLoginForm(model: Model, error: String, session: HttpSession): String
-    + home(model: Model, principal: Principal): String
-}
-
-class RestApiController {
-    - apiKeyService: ApiKeyService
-    - restApiService: RestApiService
-    + getPlayers(response: HttpServletResponse, params: Map<String, String>): String
-    + getQuestions(response: HttpServletResponse, params: Map<String, String>): String
-    + getApiKeyFromParams(params: Map<String, String>): String
-}
-
 class SignUpValidator {
     - playerService: PlayerService
     + supports(clazz: Class<?>): boolean
@@ -352,14 +291,6 @@ JsonEntity <|.. Category
 JsonEntity <|.. GameSession
 JsonEntity <|.. Player
 JsonEntity <|.. Question
-AnswerRepository --|> CrudRepository
-ApiKeyRepository --|> CrudRepository
-CategoryRepository --|> CrudRepository
-GameSessionRepository --|> CrudRepository
-PlayerRepository --|> CrudRepository
-QuestionRepository --|> CrudRepository
-RestApiLogRepository --|> CrudRepository
-RoleRepository --|> CrudRepository
 AnswerService <|.. AnswerServiceImpl
 ApiKeyService <|.. ApiKeyServiceImpl
 CategoryService <|.. CategoryServiceImpl
@@ -382,49 +313,27 @@ PlayerService ..> PlayerDto
 PlayerService ..> Player
 QuestionService ..> Question
 RestApiService ..> ApiKey
-CustomUserDetailsService "1" *- "1" PlayerRepository
 CustomUserDetailsService ..> Player
 CustomUserDetailsService ..> Role
 InsertSampleDataService "1" *- "1" PlayerService
 InsertSampleDataService "1" *- "1" QuestionService
 InsertSampleDataService "1" *- "1" CategoryService
-InsertSampleDataService "1" *- "1" QuestionRepository
-InsertSampleDataService "1" *- "1" GameSessionRepository
 InsertSampleDataService ..> PlayerDto
 InsertSampleDataService ..> GameSession
 InsertSampleDataService ..> QuestionGenerator
-AnswerServiceImpl "1" *- "1" AnswerRepository
-ApiKeyServiceImpl "1" *- "1" ApiKeyRepository
-CategoryServiceImpl "1" *- "1" CategoryRepository
-PlayerServiceImpl "1" *- "1" PlayerRepository
 PlayerServiceImpl "1" *- "1" RoleService
 PlayerServiceImpl "1" *- "1" PasswordEncoder
 PlayerServiceImpl ..> Role
-QuestionServiceImpl "1" *- "1" QuestionRepository
 RestApiServiceImpl "1" *- "1" PlayerService
-RestApiServiceImpl "1" *- "1" RestApiLogRepository
 RestApiServiceImpl "1" *- "1" QuestionService
 RestApiServiceImpl ..> Player
 RestApiServiceImpl ..> Question
-RoleServiceImpl "1" *- "1" RoleRepository
 RestApiServiceImpl ..> Role
-AnswerRepository ..> Question
-RestApiLogRepository ..> ApiKey
-RestApiLogRepository ..> Player
 Answer "*" - "1" Question
 ApiKey "1" - "1" Player
 ApiKey "1" - "*" RestApiAccessLog
 Category "1" - "*" Question
 Player "1" - "*" GameSession
-HomeController "1" *- "1" PlayerService
-PlayersController "1" *- "1" PlayerService
-PlayersController "1" *- "1" SignUpValidator
-PlayersController ..> PlayerDto
-RestApiController "1" *- "1" ApiKeyService
-RestApiController "1" *- "1" RestApiService
-RestApiController ..> ApiKey
-RestApiController ..> Player
-RestApiController ..> Question
 QuestionGeneratorTestController "1" *- "1" CapitalQuestionGenerator
 QuestionGeneratorTestController ..> Question
 AbstractQuestionGenerator "1" - "*" Question
@@ -481,10 +390,6 @@ class CustomConfiguration {
     + addInterceptors(registry: InterceptorRegistry): void
 }
 
-class CustomErrorController {
-    + error(model: Model, webRequest: HttpServletRequest): String
-}
-
 class WiqEs04bApplication {
     + main(args: String[]): void
 }
@@ -495,7 +400,6 @@ SecurityConfig "1" *- "1" UserDetailsService
 SecurityConfig "1" *- "1" CustomAuthenticationFailureHandler
 CustomAuthenticationFailureHandler --|> SimpleUrlAuthenticationFailureHandler
 WebMvcConfigurer <|.. CustomConfiguration
-CustomErrorController --|> BasicErrorController
 
 @enduml
 ----