diff --git a/service/src/app.module.ts b/service/src/app.module.ts
index 0d05ae0..8ee1998 100644
--- a/service/src/app.module.ts
+++ b/service/src/app.module.ts
@@ -1,12 +1,14 @@
 import { Module } from '@nestjs/common';
 import { ConfigModule, ConfigService } from '@nestjs/config';
-import { AppController } from './app.controller';
-import { AppService } from './app.service';
+import { AppController } from './app/app.controller';
+import { AppService } from './app/app.service';
 import { createDbClient } from './db';
+import { CalendarController } from './calendar/calendar.controller';
+import { CalendarService } from './calendar/calendar.service';
 
 @Module({
   imports: [ConfigModule.forRoot({ ignoreEnvFile: true })],
-  controllers: [AppController],
+  controllers: [AppController, CalendarController],
   providers: [
     {
       provide: 'dbClient',
@@ -18,6 +20,7 @@ import { createDbClient } from './db';
       inject: [ConfigService],
     },
     AppService,
+    CalendarService,
   ],
 })
 // eslint-disable-next-line @typescript-eslint/no-extraneous-class
diff --git a/service/src/app.controller.spec.ts b/service/src/app/app.controller.spec.ts
similarity index 96%
rename from service/src/app.controller.spec.ts
rename to service/src/app/app.controller.spec.ts
index 54a1537..84f9bba 100644
--- a/service/src/app.controller.spec.ts
+++ b/service/src/app/app.controller.spec.ts
@@ -1,7 +1,7 @@
 import { Test, TestingModule } from '@nestjs/testing';
 import { AppController } from './app.controller';
 import { AppService } from './app.service';
-import { DbClient } from './db';
+import { DbClient } from '../db';
 
 describe('AppController', () => {
   let appController: AppController;
diff --git a/service/src/app.controller.ts b/service/src/app/app.controller.ts
similarity index 100%
rename from service/src/app.controller.ts
rename to service/src/app/app.controller.ts
diff --git a/service/src/app.service.ts b/service/src/app/app.service.ts
similarity index 90%
rename from service/src/app.service.ts
rename to service/src/app/app.service.ts
index e5397d0..ca5a23c 100644
--- a/service/src/app.service.ts
+++ b/service/src/app/app.service.ts
@@ -1,5 +1,5 @@
 import { Inject, Injectable } from '@nestjs/common';
-import { DbClient } from './db';
+import { DbClient } from '../db';
 
 @Injectable()
 export class AppService {
diff --git a/service/src/calendar/calendar.controller.spec.ts b/service/src/calendar/calendar.controller.spec.ts
new file mode 100644
index 0000000..e7eb2cd
--- /dev/null
+++ b/service/src/calendar/calendar.controller.spec.ts
@@ -0,0 +1,20 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { CalendarController } from './calendar.controller';
+import { CalendarService } from './calendar.service';
+
+describe('CalendarController', () => {
+  let controller: CalendarController;
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      controllers: [CalendarController],
+      providers: [CalendarService],
+    }).compile();
+
+    controller = module.get<CalendarController>(CalendarController);
+  });
+
+  it('should be defined', () => {
+    expect(controller).toBeDefined();
+  });
+});
diff --git a/service/src/calendar/calendar.controller.ts b/service/src/calendar/calendar.controller.ts
new file mode 100644
index 0000000..b0e04c4
--- /dev/null
+++ b/service/src/calendar/calendar.controller.ts
@@ -0,0 +1,24 @@
+import {
+  Body,
+  ClassSerializerInterceptor,
+  Controller,
+  HttpCode,
+  Post,
+  UseInterceptors,
+} from '@nestjs/common';
+import { CalendarService } from './calendar.service';
+import { QueryParamsDto, QueryResponseDto } from './calendar.dto';
+
+@Controller('calendar')
+export class CalendarController {
+  constructor(private readonly calendarService: CalendarService) {}
+
+  @Post('query')
+  @HttpCode(200)
+  @UseInterceptors(ClassSerializerInterceptor)
+  async getAvailableSlots(
+    @Body() queryParamsDto: QueryParamsDto,
+  ): Promise<QueryResponseDto[]> {
+    return await this.calendarService.getAvailableSlots(queryParamsDto);
+  }
+}
diff --git a/service/src/calendar/calendar.dto.ts b/service/src/calendar/calendar.dto.ts
new file mode 100644
index 0000000..6989975
--- /dev/null
+++ b/service/src/calendar/calendar.dto.ts
@@ -0,0 +1,48 @@
+import { Expose, Transform } from 'class-transformer';
+import { IsArray, IsDateString, IsEnum, MaxLength } from 'class-validator';
+
+export enum ProductType {
+  SolarPanels = 'SolarPanels',
+  Heatpumps = 'Heatpumps',
+}
+
+export enum Language {
+  German = 'German',
+  English = 'English',
+}
+
+export enum CustomerRating {
+  Gold = 'Gold',
+  Silver = 'Silver',
+  Bronze = 'Bronze',
+}
+
+export class QueryParamsDto {
+  @MaxLength(10)
+  @IsDateString({ strict: true })
+  public date!: string;
+
+  @IsArray()
+  @IsEnum(ProductType, { each: true })
+  public products!: ProductType[];
+
+  @IsEnum(Language)
+  public language!: Language;
+
+  @IsEnum(CustomerRating)
+  public rating!: CustomerRating;
+}
+
+export class QueryResponseDto {
+  @Expose({ name: 'available_count' })
+  availableCount: number;
+
+  @Expose({ name: 'start_date' })
+  @Transform(({ value }) => (value as Date).toISOString())
+  startDate: Date;
+
+  constructor(availableCount: number, startDate: Date) {
+    this.availableCount = availableCount;
+    this.startDate = startDate;
+  }
+}
diff --git a/service/src/calendar/calendar.service.spec.ts b/service/src/calendar/calendar.service.spec.ts
new file mode 100644
index 0000000..1927e6a
--- /dev/null
+++ b/service/src/calendar/calendar.service.spec.ts
@@ -0,0 +1,18 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { CalendarService } from './calendar.service';
+
+describe('CalendarService', () => {
+  let service: CalendarService;
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [CalendarService],
+    }).compile();
+
+    service = module.get<CalendarService>(CalendarService);
+  });
+
+  it('should be defined', () => {
+    expect(service).toBeDefined();
+  });
+});
diff --git a/service/src/calendar/calendar.service.ts b/service/src/calendar/calendar.service.ts
new file mode 100644
index 0000000..9d29df8
--- /dev/null
+++ b/service/src/calendar/calendar.service.ts
@@ -0,0 +1,10 @@
+import { Injectable } from '@nestjs/common';
+import { QueryParamsDto, QueryResponseDto } from './calendar.dto';
+
+@Injectable()
+export class CalendarService {
+  async getAvailableSlots(queryParamsDto: QueryParamsDto) {
+    console.log(queryParamsDto);
+    return Promise.resolve([new QueryResponseDto(1, new Date())]);
+  }
+}