diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..39c21f5
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,15 @@
+# http://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true
+
+[{*.java,*.kt}]
+# See https://github.com/shyiko/ktlint/issues/47#issuecomment-317333157
+max_line_length = 100
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6e73db9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,68 @@
+# Created by https://www.gitignore.io/api/java,gradle,kotlin
+
+### Java ###
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+.idea/
+
+out/
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+### Kotlin ###
+# Compiled class file
+
+# Log file
+
+# BlueJ files
+
+# Mobile Tools for Java (J2ME)
+
+# Package Files #
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+
+### Gradle ###
+.gradle
+/build/
+
+# Ignore Gradle GUI config
+gradle-app.setting
+
+# Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored)
+!gradle-wrapper.jar
+
+# Cache of project
+.gradletasknamecache
+
+# # Work around https://youtrack.jetbrains.com/issue/IDEA-116898
+# gradle/wrapper/gradle-wrapper.properties
+
+
+# Intellij files
+*.iml
+
+# Mac
+.DS_Store
+
+# End of https://www.gitignore.io/api/java,gradle,kotlin
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..39e5118
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2018 Dirk-Jan Rutten
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..08f25d3
--- /dev/null
+++ b/README.md
@@ -0,0 +1,19 @@
+# README
+Adopted and modified from : https://github.com/excitement-engineer/ktor-graphql
+
+## About
+This is a graphql backend for a small social networking app.
+
+## Data model
+Can be found in `schema.graphql`
+
+## Execution strategies
+For simplicity, we are using singletons to simulate our data access layers. 
+In the real world, usage of dataloaders is recommended. Read more about that [here](https://www.graphql-java.com/documentation/v12/batching/)
+
+## Technical
+Although this example uses Ktor, any Kotlin server may be used.
+
+## Schema first vs code first
+This example is schema first, but there are also possibilities to write code-first resolvers 
+(aka schema is defined by the code). Examples of code-first can be found [here](https://github.com/ExpediaDotCom/graphql-kotlin)
diff --git a/build.gradle b/build.gradle
new file mode 100644
index 0000000..6d083cd
--- /dev/null
+++ b/build.gradle
@@ -0,0 +1,63 @@
+buildscript {
+  ext.kotlin_version = '1.5.10'
+  ext.ktor_version = '1.1.1'
+
+  repositories {
+    mavenCentral()
+  }
+  dependencies {
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.10"
+    classpath 'org.junit.platform:junit-platform-gradle-plugin:1.2.0'
+  }
+}
+
+plugins {
+  id 'application'
+  id "com.github.ben-manes.versions" version "0.39.0"
+}
+
+
+group 'ktor-graphql-example'
+version '1.0'
+
+apply plugin: 'kotlin'
+apply plugin: 'org.junit.platform.gradle.plugin'
+
+repositories {
+  mavenCentral()
+}
+
+dependencies {
+  implementation "com.github.excitement-engineer:ktor-graphql:2.1.0"
+  implementation "com.graphql-java-kickstart:graphql-java-tools:11.0.1"
+  implementation "org.jetbrains.kotlin:kotlin-stdlib:1.5.10"
+  implementation "com.google.code.gson:gson:2.8.7"
+  implementation "com.graphql-java:graphql-java:16.2"
+  implementation 'com.graphql-java:graphql-java-extended-scalars:16.0.1'
+  implementation 'com.google.guava:guava:30.1.1-jre'
+  implementation 'com.github.javafaker:javafaker:1.0.2'
+  implementation "io.ktor:ktor-server-netty:1.6.0"
+  implementation 'com.graphql-java:java-dataloader:2.2.3'
+  implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.5.0'
+  implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-slf4j:1.5.0'
+}
+
+compileKotlin {
+  kotlinOptions.jvmTarget = "11"
+}
+compileTestKotlin {
+  kotlinOptions.jvmTarget = "11"
+}
+
+junitPlatform {
+  filters {
+    engines {
+      include 'spek'
+    }
+  }
+}
+task stage(dependsOn: ['build', 'clean'])
+
+application {
+  mainClassName = 'Application'
+}
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..457aad0
Binary files /dev/null and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..bb9ea7f
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,6 @@
+#Tue Jun 08 16:35:52 CEST 2021
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.0.2-all.zip
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStorePath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
diff --git a/gradlew b/gradlew
new file mode 100755
index 0000000..af6708f
--- /dev/null
+++ b/gradlew
@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
new file mode 100644
index 0000000..0f8d593
--- /dev/null
+++ b/gradlew.bat
@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/renovate.json5 b/renovate.json5
new file mode 100644
index 0000000..c5974f9
--- /dev/null
+++ b/renovate.json5
@@ -0,0 +1,25 @@
+{
+  "branchPrefix": "renovate-",
+  "dependencyDashboard": true,
+  "extends": [
+    "config:base"
+  ],
+  // Ensure that major is never automerged
+  "major": {
+    "automerge": false
+  },
+  "packageRules": [
+    {
+      "description": "Avoid updates such as from 14.1 to 2020-06-07T01-00-15-98bb45a",
+      "packagePatterns": ["^com\\.graphql-java:"],
+      "versioning": "semver"
+    }
+  ],
+  // Default 0, but use this to prevent renovate from spamming PRs
+  "prConcurrentLimit": 0,
+  "schedule": [
+    "every weekday"
+  ],
+  "stabilityDays": 10,
+  "timezone": "Europe/Oslo"
+}
diff --git a/settings.gradle b/settings.gradle
new file mode 100644
index 0000000..23f23db
--- /dev/null
+++ b/settings.gradle
@@ -0,0 +1,2 @@
+rootProject.name = 'com.github.excitement-engineer'
+
diff --git a/src/main/kotlin/ClientException.kt b/src/main/kotlin/ClientException.kt
new file mode 100644
index 0000000..786c2a2
--- /dev/null
+++ b/src/main/kotlin/ClientException.kt
@@ -0,0 +1 @@
+class ClientException(message: String) : Exception(message)
\ No newline at end of file
diff --git a/src/main/kotlin/Dataloaders.kt b/src/main/kotlin/Dataloaders.kt
new file mode 100644
index 0000000..e1e6710
--- /dev/null
+++ b/src/main/kotlin/Dataloaders.kt
@@ -0,0 +1,59 @@
+import graphql.schema.DataFetchingEnvironment
+import kotlinx.coroutines.future.future
+import org.dataloader.DataLoader
+import org.dataloader.DataLoaderRegistry
+import kotlin.coroutines.CoroutineContext
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.slf4j.MDCContext
+import org.dataloader.BatchLoader
+
+fun buildRegistry() = DataLoaderRegistry().apply {
+  register(PetBatchLoader.key, DataLoader(PetBatchLoader()))
+  register(PersonBatchLoader.key, DataLoader(PersonBatchLoader()))
+}
+
+object PersonBatchLoader : CoroutineScope {
+  override val coroutineContext: CoroutineContext
+    get() = MDCContext()
+
+  operator fun invoke() =
+    BatchLoader<Int, Person> { keys ->
+      future(coroutineContext) {
+        val people = PersonRepository.findByIds(keys).associateBy { it.id }
+        keys
+          .map {
+            people.getValue(it)
+          }
+      }
+    }
+
+  const val key = "Person"
+}
+
+object PetBatchLoader : CoroutineScope {
+  override val coroutineContext: CoroutineContext
+    get() = MDCContext()
+
+  operator fun invoke() =
+    BatchLoader<Int, Pet> { keys ->
+      future(coroutineContext) {
+        val pets = PetsRepository.findByIds(keys).associateBy { it.id }
+        keys
+          .map {
+            pets.getValue(it)
+          }
+      }
+    }
+
+  const val key = "Pet"
+}
+
+// Define loader as extension method to ensure types are used consistently.
+fun DataFetchingEnvironment.getPersonDataLoader(): DataLoader<Int, Person> =
+  dataLoaderRegistry
+    .getDataLoader(PersonBatchLoader.key)
+
+fun DataFetchingEnvironment.getPetDataLoader(): DataLoader<Int, Pet> =
+  dataLoaderRegistry
+    .getDataLoader(PetBatchLoader.key)
+
diff --git a/src/main/kotlin/Inputs.kt b/src/main/kotlin/Inputs.kt
new file mode 100644
index 0000000..3cc5cdf
--- /dev/null
+++ b/src/main/kotlin/Inputs.kt
@@ -0,0 +1,12 @@
+data class PersonInput(
+  val name: String
+)
+
+data class SearchInput(
+  val queryString: String
+)
+
+data class AddFriendsInput(
+  val first: Int,
+  val second: Int
+)
diff --git a/src/main/kotlin/Payload.kt b/src/main/kotlin/Payload.kt
new file mode 100644
index 0000000..7f3b24d
--- /dev/null
+++ b/src/main/kotlin/Payload.kt
@@ -0,0 +1,6 @@
+data class WipeDataPayload(val success: Boolean) {
+  companion object {
+    val SUCCESS = WipeDataPayload(true)
+    val FAILURE = WipeDataPayload(false)
+  }
+}
diff --git a/src/main/kotlin/Person.kt b/src/main/kotlin/Person.kt
new file mode 100644
index 0000000..15afe16
--- /dev/null
+++ b/src/main/kotlin/Person.kt
@@ -0,0 +1,32 @@
+import com.github.javafaker.Faker
+import graphql.schema.DataFetchingEnvironment
+import java.text.SimpleDateFormat
+import java.util.concurrent.CompletableFuture
+
+@Suppress("unused") // GraphQL by reflection
+data class Person(
+  val id: Int, // modified for simplicity
+  val name: String,
+  val petIds: List<Int> = emptyList()
+) : Searchable {
+
+  private val friendIds = mutableListOf<Int>()
+  override fun matches(queryString: String) = name.contains(queryString)
+
+  val dateOfBirth = SimpleDateFormat("yyyy-MM-dd")
+    .format(Faker().date().birthday())
+    .replace("(\\d\\d)(\\d\\d)$", "$1:$2")
+
+  val description = Faker().lorem().paragraphs(2).joinToString("\n")
+
+  fun friends(env: DataFetchingEnvironment): CompletableFuture<List<Person>> =
+    env.getPersonDataLoader().loadMany(friendIds)
+
+  fun pets(env: DataFetchingEnvironment): CompletableFuture<List<Pet>> =
+    env.getPetDataLoader().loadMany(petIds)
+
+  fun addFriend(other: Person) =
+    if (friendIds.contains(other.id)) true
+    else friendIds.add(other.id)
+
+}
diff --git a/src/main/kotlin/PersonRepository.kt b/src/main/kotlin/PersonRepository.kt
new file mode 100644
index 0000000..0ee50d6
--- /dev/null
+++ b/src/main/kotlin/PersonRepository.kt
@@ -0,0 +1,34 @@
+object PersonRepository {
+  var people: MutableList<Person> = mutableListOf()
+
+  fun clear() = people.clear()
+
+  fun addPerson(name: String): Person {
+    val id = nextId()
+    val person = Person(id, name, emptyList())
+    people.add(person)
+    return person
+  }
+
+  fun addPerson(person: Person) =
+    if (people.find { it.id == person.id } != null)
+      throw IllegalArgumentException("Already one person with that ID")
+    else
+      people.add(person)
+
+  fun addFriends(first: Person, second: Person): Boolean =
+    first.addFriend(second) && second.addFriend(first)
+
+  fun allPeople() = people.toList().also {
+    println("Expensive call to get all people")
+  }
+
+  // Note: this can be expensive, so look at the Person.kt class for a hint on how to batch calls
+  fun findById(id: Int) = people.first { it.id == id }
+
+  fun findByIds(ids: List<Int>) = people.filter { it.id in ids }.also {
+    println("An expensive call to find the people with id $ids")
+  }
+
+  fun nextId() = (people.maxByOrNull { it.id }?.id ?: 0) + 1
+}
diff --git a/src/main/kotlin/Pets.kt b/src/main/kotlin/Pets.kt
new file mode 100644
index 0000000..aa5ba55
--- /dev/null
+++ b/src/main/kotlin/Pets.kt
@@ -0,0 +1,24 @@
+sealed class Pet: Searchable {
+  abstract val id: Int
+  abstract val name: String
+  abstract fun makeSound(): String
+  override fun matches(queryString: String) = name.contains(queryString)
+}
+
+@Suppress("unused") // GraphQL by reflection
+data class Dog(
+  override val id: Int,
+  override val name: String
+): Pet() {
+  override fun makeSound() = "bark"
+  fun barkLoudly() = "WOOF WOOF"
+}
+
+@Suppress("unused") // GraphQL by reflection
+data class Cat(
+  override val id: Int,
+  override val name: String
+): Pet() {
+  override fun makeSound() = "purr"
+  fun beLazy() = ""
+}
diff --git a/src/main/kotlin/PetsRepository.kt b/src/main/kotlin/PetsRepository.kt
new file mode 100644
index 0000000..1d1513d
--- /dev/null
+++ b/src/main/kotlin/PetsRepository.kt
@@ -0,0 +1,22 @@
+object PetsRepository {
+  var pets = mutableListOf<Pet>()
+
+  fun clear() = pets.clear()
+
+  fun findById(id: Int) = pets.first { it.id == id }
+  fun findByIds(ids: List<Int>) = pets
+    .filter { it.id in ids}
+    .also {
+      println("Another expensive call to get pets with ids: $ids")
+    }
+
+  fun allPets() = pets.toList()
+
+  fun addPet(pet: Pet) =
+    if (pets.find { it.id == pet.id } != null)
+      throw IllegalArgumentException("Already exists")
+    else
+      pets.add(pet)
+
+  fun nextId() = (pets.maxByOrNull { it.id }?.id ?: 0) + 1
+}
diff --git a/src/main/kotlin/Searchable.kt b/src/main/kotlin/Searchable.kt
new file mode 100644
index 0000000..44220c1
--- /dev/null
+++ b/src/main/kotlin/Searchable.kt
@@ -0,0 +1,3 @@
+interface Searchable {
+  fun matches(queryString: String): Boolean
+}
\ No newline at end of file
diff --git a/src/main/kotlin/formatGraphQLError.kt b/src/main/kotlin/formatGraphQLError.kt
new file mode 100644
index 0000000..a4ee61d
--- /dev/null
+++ b/src/main/kotlin/formatGraphQLError.kt
@@ -0,0 +1,21 @@
+import graphql.ExceptionWhileDataFetching
+import graphql.GraphQLError
+
+val formatErrorGraphQLError: (GraphQLError.() -> Map<String, Any>) = {
+  val clientMessage = if (this is ExceptionWhileDataFetching) {
+
+    val formattedMessage = if (exception is ClientException) {
+      exception.message
+    } else {
+      "Internal server error"
+    }
+
+    formattedMessage
+  } else {
+    message
+  }
+
+  val result = toSpecification()
+  result["message"] = clientMessage
+  result
+}
\ No newline at end of file
diff --git a/src/main/kotlin/main.kt b/src/main/kotlin/main.kt
new file mode 100644
index 0000000..ccd71b6
--- /dev/null
+++ b/src/main/kotlin/main.kt
@@ -0,0 +1,7 @@
+import io.ktor.application.Application
+import io.ktor.server.engine.embeddedServer
+import io.ktor.server.netty.Netty
+
+fun main() {
+  embeddedServer(Netty, port = 8080, module = Application::main).start(wait = true)
+}
\ No newline at end of file
diff --git a/src/main/kotlin/schema.kt b/src/main/kotlin/schema.kt
new file mode 100644
index 0000000..6a63fc6
--- /dev/null
+++ b/src/main/kotlin/schema.kt
@@ -0,0 +1,95 @@
+import com.github.javafaker.Faker
+import graphql.kickstart.tools.GraphQLMutationResolver
+import graphql.kickstart.tools.GraphQLQueryResolver
+import graphql.kickstart.tools.SchemaParser
+import com.google.common.io.Resources
+import graphql.scalars.ExtendedScalars
+import kotlin.random.Random
+
+val schema = createExecutableSchema()
+
+@Suppress("UnstableApiUsage")
+fun createExecutableSchema() = SchemaParser
+  .newParser()
+  .schemaString(
+    Resources.toString(
+      Resources.getResource("schema.graphql"),
+      Charsets.UTF_8
+    )
+  )
+  .dictionary( // Currently required for sealed classes
+    mapOf(
+      "Cat" to Cat::class.java,
+      "Dog" to Dog::class.java
+    )
+  )
+  .scalars(ExtendedScalars.Date)
+  .resolvers(QueryResolver(), MutationResolver())
+  .build()
+  .makeExecutableSchema()
+
+@Suppress("unused") // GraphQL by reflection
+class QueryResolver : GraphQLQueryResolver {
+  fun person(id: Int) = PersonRepository.findById(id)
+  fun allPeople() = PersonRepository.allPeople()
+  fun search(input: SearchInput): List<Any> =
+    (PersonRepository.allPeople() + PetsRepository.allPets()).filter {
+      it.matches(input.queryString)
+    }
+}
+
+@Suppress("unused") // GraphQL by reflection
+class MutationResolver : GraphQLMutationResolver {
+  fun wipeData() = run {
+    try {
+      PersonRepository.clear()
+      PetsRepository.clear()
+      WipeDataPayload.SUCCESS
+    } catch (e: Exception) {
+      WipeDataPayload.FAILURE
+    }
+  }
+
+  fun generateData(): List<Person> {
+    val faker = Faker()
+    val newPeople = (1..10).map {
+      val fakePersonName = faker.name().nameWithMiddle()
+
+      val petIds = (0..Random.nextInt(5)).map {
+        val petId = PetsRepository.nextId()
+        val pet = when (Random.nextInt(2)) {
+          0 -> Dog(petId, faker.dog().name())
+          else -> Cat(petId, faker.cat().name())
+        }
+        PetsRepository.addPet(pet)
+        pet.id
+      }
+
+      val person = Person(
+        PersonRepository.nextId(),
+        fakePersonName,
+        petIds
+      )
+      PersonRepository.addPerson(person)
+
+      person
+    }
+
+    val allPeople = PersonRepository.allPeople()
+
+    newPeople.forEach { newPerson ->
+      val anotherPerson = allPeople.minus(newPerson).random()
+      PersonRepository.addFriends(newPerson, anotherPerson)
+    }
+
+    return newPeople
+  }
+
+  fun addPerson(input: PersonInput): Person = PersonRepository.addPerson(input.name)
+  fun addFriends(input: AddFriendsInput): Boolean {
+    val first = PersonRepository.findById(input.first)
+    val second = PersonRepository.findById(input.second)
+
+    return PersonRepository.addFriends(first, second)
+  }
+}
diff --git a/src/main/kotlin/server.kt b/src/main/kotlin/server.kt
new file mode 100644
index 0000000..baddd8a
--- /dev/null
+++ b/src/main/kotlin/server.kt
@@ -0,0 +1,36 @@
+import graphql.ExecutionInput
+import graphql.GraphQL
+import io.ktor.application.Application
+import io.ktor.routing.routing
+import io.ktor.server.engine.embeddedServer
+import io.ktor.server.netty.Netty
+import ktor.graphql.Config
+import ktor.graphql.fromRequest
+import ktor.graphql.graphQL
+
+fun Application.main() {
+  val graphQLExecutor = GraphQL.newGraphQL(schema).build()
+
+  val server = embeddedServer(Netty, port = 8080) {
+    routing {
+      graphQL("/graphql", schema) { request ->
+        Config(
+          formatError = formatErrorGraphQLError,
+          showExplorer = true,
+          executeRequest = {
+            // Building registry per request ensures that we don't share data across requests
+            val dataloaderRegistry = buildRegistry()
+            val input = ExecutionInput.newExecutionInput()
+              .fromRequest(request)
+              .dataLoaderRegistry(dataloaderRegistry)
+              .build()
+
+            graphQLExecutor.execute(input)
+          }
+        )
+      }
+    }
+  }
+
+  server.start(wait = true)
+}
diff --git a/src/main/resources/schema.graphql b/src/main/resources/schema.graphql
new file mode 100644
index 0000000..0b08962
--- /dev/null
+++ b/src/main/resources/schema.graphql
@@ -0,0 +1,62 @@
+input AddFriendsInput {
+  first: ID!
+  second: ID!
+}
+
+type Cat implements Pet {
+  id: ID!
+  name: String!
+  makeSound: String!
+  beLazy: String!
+}
+
+type Dog implements Pet {
+  id: ID!
+  name: String!
+  makeSound: String!
+  barkLoudly: String!
+}
+
+interface Pet {
+  id: ID!
+  name: String!
+  makeSound: String!
+}
+
+type Person {
+  id: ID!
+  name: String!
+  description: String!
+  dateOfBirth: Date!
+  friends: [Person!]!
+  pets: [Pet!]!
+}
+
+input PersonInput {
+  name: String!
+}
+
+union SearchResult = Dog | Cat | Person
+input SearchInput {
+  queryString: String!
+}
+
+type Query {
+  allPeople: [Person!]!
+  person(id: ID!): Person!
+  search(input: SearchInput!): [SearchResult!]!
+}
+
+type Mutation {
+  addPerson(input: PersonInput!): Person!
+  addFriends(input: AddFriendsInput!): Boolean!
+  generateData: [Person!]!
+  wipeData: WipeDataPayload!
+}
+
+type WipeDataPayload {
+  success: Boolean!
+}
+
+# RFC3339: full-date
+scalar Date