diff --git a/apollo-graphql/client/package-lock.json b/apollo-graphql/client/package-lock.json
index d4b182f..4753449 100644
--- a/apollo-graphql/client/package-lock.json
+++ b/apollo-graphql/client/package-lock.json
@@ -13,6 +13,7 @@
         "@testing-library/react": "^12.1.2",
         "@testing-library/user-event": "^13.5.0",
         "graphql": "^16.6.0",
+        "graphql-ws": "^5.12.1",
         "react": "^18.1.0",
         "react-dom": "^18.1.0",
         "react-scripts": "5.0.0",
@@ -7925,6 +7926,17 @@
         "graphql": "^0.9.0 || ^0.10.0 || ^0.11.0 || ^0.12.0 || ^0.13.0 || ^14.0.0 || ^15.0.0 || ^16.0.0"
       }
     },
+    "node_modules/graphql-ws": {
+      "version": "5.12.1",
+      "resolved": "https://registry.npmjs.org/graphql-ws/-/graphql-ws-5.12.1.tgz",
+      "integrity": "sha512-umt4f5NnMK46ChM2coO36PTFhHouBrK9stWWBczERguwYrGnPNxJ9dimU6IyOBfOkC6Izhkg4H8+F51W/8CYDg==",
+      "engines": {
+        "node": ">=10"
+      },
+      "peerDependencies": {
+        "graphql": ">=0.11 <=16"
+      }
+    },
     "node_modules/gzip-size": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/gzip-size/-/gzip-size-6.0.0.tgz",
@@ -21805,6 +21817,12 @@
         "tslib": "^2.1.0"
       }
     },
+    "graphql-ws": {
+      "version": "5.12.1",
+      "resolved": "https://registry.npmjs.org/graphql-ws/-/graphql-ws-5.12.1.tgz",
+      "integrity": "sha512-umt4f5NnMK46ChM2coO36PTFhHouBrK9stWWBczERguwYrGnPNxJ9dimU6IyOBfOkC6Izhkg4H8+F51W/8CYDg==",
+      "requires": {}
+    },
     "gzip-size": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/gzip-size/-/gzip-size-6.0.0.tgz",
diff --git a/apollo-graphql/client/package.json b/apollo-graphql/client/package.json
index c124437..2c22edc 100644
--- a/apollo-graphql/client/package.json
+++ b/apollo-graphql/client/package.json
@@ -8,6 +8,7 @@
     "@testing-library/react": "^12.1.2",
     "@testing-library/user-event": "^13.5.0",
     "graphql": "^16.6.0",
+    "graphql-ws": "^5.12.1",
     "react": "^18.1.0",
     "react-dom": "^18.1.0",
     "react-scripts": "5.0.0",
diff --git a/apollo-graphql/client/src/App.js b/apollo-graphql/client/src/App.js
index e1d08ab..d49db1f 100644
--- a/apollo-graphql/client/src/App.js
+++ b/apollo-graphql/client/src/App.js
@@ -1,18 +1,26 @@
 import { useState  } from 'react';
-import { useQuery, useApolloClient } from '@apollo/client';
+import { useQuery, useApolloClient, useSubscription } from '@apollo/client';
 import './App.css';
-import { ALL_PERSONS } from './queries/queries';
+import { ALL_PERSONS, PERSON_ADDED } from './queries/queries';
 import { Persons } from './Persons';
 import { PersonForm } from './forms/PersonForm';
 import { PhoneForm } from './forms/PhoneForm';
 import { Notify  } from './components/Notify';
 import { LoginForm } from './forms/LoginForm';
+import { updateCache } from './utils/updateCache';
 
 function App() {
   const [token, setToken] = useState(null);
   const [errorMsg, setErrorMsg] = useState('');
   const result = useQuery(ALL_PERSONS);
   const client = useApolloClient();
+  useSubscription(PERSON_ADDED, {
+    onData: ({ data }) => {
+      const addedPerson = data.data.personAdded
+      notify(`${addedPerson.name} added`)
+      updateCache(client.cache, { query: ALL_PERSONS }, addedPerson)
+    }
+  })
   
   const notify = (message) => {
     setErrorMsg(message);
diff --git a/apollo-graphql/client/src/forms/LoginForm.js b/apollo-graphql/client/src/forms/LoginForm.js
index 3812d66..ed792c4 100644
--- a/apollo-graphql/client/src/forms/LoginForm.js
+++ b/apollo-graphql/client/src/forms/LoginForm.js
@@ -1,6 +1,6 @@
 import { useState, useEffect } from 'react';
 import { useMutation } from '@apollo/client';
-import { LOGIN } from '../queries';
+import { LOGIN } from '../queries/queries';
 
 export   const LoginForm = props => {
   const [username, setUsername] = useState('');
diff --git a/apollo-graphql/client/src/forms/PersonForm.js b/apollo-graphql/client/src/forms/PersonForm.js
index 2d974e6..c0c0557 100644
--- a/apollo-graphql/client/src/forms/PersonForm.js
+++ b/apollo-graphql/client/src/forms/PersonForm.js
@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { useMutation } from '@apollo/client';
 import { ALL_PERSONS, ADD_PERSON } from '../queries/queries';
+import { updateCache } from '../utils/updateCache';
 
 export const PersonForm = props => {
   const [name, setName] = useState('');
@@ -15,11 +16,7 @@ export const PersonForm = props => {
       props.setError(message);
     },
     update: (cache, response) => {
-      cache.updateQuery({ query: ALL_PERSONS }, ({ allPersons }) => {
-        return {
-          allPersons: allPersons.concat(response.data.addNewPerson),
-        }
-      })
+      updateCache(cache, { query: ALL_PERSONS }, response.data.addPerson)
     }
   });
 
diff --git a/apollo-graphql/client/src/forms/PhoneForm.js b/apollo-graphql/client/src/forms/PhoneForm.js
index 30f1303..31c1444 100644
--- a/apollo-graphql/client/src/forms/PhoneForm.js
+++ b/apollo-graphql/client/src/forms/PhoneForm.js
@@ -1,13 +1,12 @@
-import { useState , useEffect } from 'react'
-import { useMutation } from '@apollo/client'
-
-import { EDIT_NUMBER } from '../queries'
+import { useState , useEffect } from 'react';
+import { useMutation } from '@apollo/client';
+import { UPDATE_PHONE } from '../queries/queries';
 
 export const PhoneForm = ({ setError }) => {
   const [name, setName] = useState('')
   const [phone, setPhone] = useState('')
 
-  const [ changeNumber, result ] = useMutation(EDIT_NUMBER, {
+  const [ changeNumber, result ] = useMutation(UPDATE_PHONE, {
     onError: (error) => {
       const errors = error.graphQLErrors[0].extensions.error.errors
       const messages = Object.values(errors).map(e => e.message).join('\n')
diff --git a/apollo-graphql/client/src/index.js b/apollo-graphql/client/src/index.js
index a803b8b..c3a6691 100644
--- a/apollo-graphql/client/src/index.js
+++ b/apollo-graphql/client/src/index.js
@@ -6,9 +6,13 @@ import {
   ApolloClient,
   ApolloProvider,
   InMemoryCache,
-  createHttpLink
+  createHttpLink,
+  split
 } from '@apollo/client';
 import { setContext } from '@apollo/client/link/context';
+import { getMainDefinition } from '@apollo/client/utilities';
+import { GraphQLWsLink } from '@apollo/client/link/subscriptions';
+import { createClient } from 'graphql-ws';
 
 const authLink = setContext((_, { headers }) => {
   const token = localStorage.getItem('phonenumbers-user-token')
@@ -23,9 +27,23 @@ const authLink = setContext((_, { headers }) => {
 const httpLink = createHttpLink({
   uri: 'http://localhost:4000'
 });
+const wsLink = new GraphQLWsLink(
+  createClient({ url: 'ws://localhost:4000' })
+);
+const splitLink = split(
+  ({ query }) => {
+    const definition = getMainDefinition(query)
+    return (
+      definition.kind === 'OperationDefinition' &&
+      definition.operation === 'subscription'
+    )
+  },
+  wsLink,
+  authLink.concat(httpLink)
+)
 
 const client = new ApolloClient({
-  link: authLink.concat(httpLink),
+  link: splitLink,
   cache: new InMemoryCache(),
 })
 
diff --git a/apollo-graphql/client/src/queries/queries.js b/apollo-graphql/client/src/queries/queries.js
index c2e7ebf..045dfc3 100644
--- a/apollo-graphql/client/src/queries/queries.js
+++ b/apollo-graphql/client/src/queries/queries.js
@@ -59,3 +59,11 @@ export const LOGIN = gql`
     }
   }
 `;
+
+export const PERSON_ADDED = gql`
+  subscription {
+    personAdded {
+      ${PERSON}
+    }
+  }
+`;
diff --git a/apollo-graphql/client/src/utils/updateCache.js b/apollo-graphql/client/src/utils/updateCache.js
new file mode 100644
index 0000000..beaaf21
--- /dev/null
+++ b/apollo-graphql/client/src/utils/updateCache.js
@@ -0,0 +1,17 @@
+// function that takes care of manipulating cache
+export const updateCache = (cache, query, addedPerson) => {
+  // helper that is used to eliminate saving same person twice
+  const uniqByName = (a) => {
+    let seen = new Set();
+    return a.filter((item) => {
+      let k = item.name;
+      return seen.has(k) ? false : seen.add(k);
+    });
+  }
+;
+  cache.updateQuery(query, ({ allPersons }) => {
+    return {
+      allPersons: uniqByName(allPersons.concat(addedPerson)),
+    };
+  });
+};
diff --git a/apollo-graphql/server/models/person.js b/apollo-graphql/server/models/person.js
index 40cc1bd..ccddce6 100644
--- a/apollo-graphql/server/models/person.js
+++ b/apollo-graphql/server/models/person.js
@@ -20,6 +20,12 @@ const schema = new mongoose.Schema({
     required: true,
     minlength: 3
   },
+  friendOf: [
+    {
+      type: mongoose.Schema.Types.ObjectId,
+      ref: 'User'
+    }
+  ], 
 });
 
 module.exports = mongoose.model('Person', schema);
\ No newline at end of file
diff --git a/apollo-graphql/server/package-lock.json b/apollo-graphql/server/package-lock.json
index 4665a70..a09cd52 100644
--- a/apollo-graphql/server/package-lock.json
+++ b/apollo-graphql/server/package-lock.json
@@ -10,9 +10,16 @@
       "license": "MIT",
       "dependencies": {
         "@apollo/server": "^4.6.0",
+        "@graphql-tools/schema": "^9.0.18",
+        "cors": "^2.8.5",
         "dotenv": "^16.0.3",
+        "express": "^4.18.2",
         "graphql": "^16.6.0",
-        "mongoose": "^7.0.4"
+        "graphql-subscriptions": "^2.0.0",
+        "graphql-ws": "^5.12.1",
+        "jsonwebtoken": "^9.0.0",
+        "mongoose": "^7.0.4",
+        "ws": "^8.13.0"
       }
     },
     "node_modules/@apollo/cache-control-types": {
@@ -502,6 +509,11 @@
         "node": ">=14.20.1"
       }
     },
+    "node_modules/buffer-equal-constant-time": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/buffer-equal-constant-time/-/buffer-equal-constant-time-1.0.1.tgz",
+      "integrity": "sha512-zRpUiDwd/xk6ADqPMATG8vc9VPrkck7T07OIx0gnjmJAnHnTVXNQG3vfvWNuiZIkwu9KrKdA1iJKfsfTVxE6NA=="
+    },
     "node_modules/bytes": {
       "version": "3.1.2",
       "resolved": "https://registry.npmjs.org/bytes/-/bytes-3.1.2.tgz",
@@ -618,6 +630,14 @@
         "node": ">=12"
       }
     },
+    "node_modules/ecdsa-sig-formatter": {
+      "version": "1.0.11",
+      "resolved": "https://registry.npmjs.org/ecdsa-sig-formatter/-/ecdsa-sig-formatter-1.0.11.tgz",
+      "integrity": "sha512-nagl3RYrbNv6kQkeJIpt6NJZy8twLB/2vtz6yN9Z4vRKHN4/QZJIEbqohALSgwKdnksuY3k5Addp5lg8sVoVcQ==",
+      "dependencies": {
+        "safe-buffer": "^5.0.1"
+      }
+    },
     "node_modules/ee-first": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/ee-first/-/ee-first-1.1.1.tgz",
@@ -794,6 +814,28 @@
         "node": "^12.22.0 || ^14.16.0 || ^16.0.0 || >=17.0.0"
       }
     },
+    "node_modules/graphql-subscriptions": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/graphql-subscriptions/-/graphql-subscriptions-2.0.0.tgz",
+      "integrity": "sha512-s6k2b8mmt9gF9pEfkxsaO1lTxaySfKoEJzEfmwguBbQ//Oq23hIXCfR1hm4kdh5hnR20RdwB+s3BCb+0duHSZA==",
+      "dependencies": {
+        "iterall": "^1.3.0"
+      },
+      "peerDependencies": {
+        "graphql": "^15.7.2 || ^16.0.0"
+      }
+    },
+    "node_modules/graphql-ws": {
+      "version": "5.12.1",
+      "resolved": "https://registry.npmjs.org/graphql-ws/-/graphql-ws-5.12.1.tgz",
+      "integrity": "sha512-umt4f5NnMK46ChM2coO36PTFhHouBrK9stWWBczERguwYrGnPNxJ9dimU6IyOBfOkC6Izhkg4H8+F51W/8CYDg==",
+      "engines": {
+        "node": ">=10"
+      },
+      "peerDependencies": {
+        "graphql": ">=0.11 <=16"
+      }
+    },
     "node_modules/has": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/has/-/has-1.0.3.tgz",
@@ -860,6 +902,50 @@
         "node": ">= 0.10"
       }
     },
+    "node_modules/iterall": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/iterall/-/iterall-1.3.0.tgz",
+      "integrity": "sha512-QZ9qOMdF+QLHxy1QIpUHUU1D5pS2CG2P69LF6L6CPjPYA/XMOmKV3PZpawHoAjHNyB0swdVTRxdYT4tbBbxqwg=="
+    },
+    "node_modules/jsonwebtoken": {
+      "version": "9.0.0",
+      "resolved": "https://registry.npmjs.org/jsonwebtoken/-/jsonwebtoken-9.0.0.tgz",
+      "integrity": "sha512-tuGfYXxkQGDPnLJ7SibiQgVgeDgfbPq2k2ICcbgqW8WxWLBAxKQM/ZCu/IT8SOSwmaYl4dpTFCW5xZv7YbbWUw==",
+      "dependencies": {
+        "jws": "^3.2.2",
+        "lodash": "^4.17.21",
+        "ms": "^2.1.1",
+        "semver": "^7.3.8"
+      },
+      "engines": {
+        "node": ">=12",
+        "npm": ">=6"
+      }
+    },
+    "node_modules/jsonwebtoken/node_modules/ms": {
+      "version": "2.1.3",
+      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
+      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA=="
+    },
+    "node_modules/jwa": {
+      "version": "1.4.1",
+      "resolved": "https://registry.npmjs.org/jwa/-/jwa-1.4.1.tgz",
+      "integrity": "sha512-qiLX/xhEEFKUAJ6FiBMbes3w9ATzyk5W7Hvzpa/SLYdxNtng+gcurvrI7TbACjIXlsJyr05/S1oUhZrc63evQA==",
+      "dependencies": {
+        "buffer-equal-constant-time": "1.0.1",
+        "ecdsa-sig-formatter": "1.0.11",
+        "safe-buffer": "^5.0.1"
+      }
+    },
+    "node_modules/jws": {
+      "version": "3.2.2",
+      "resolved": "https://registry.npmjs.org/jws/-/jws-3.2.2.tgz",
+      "integrity": "sha512-YHlZCB6lMTllWDtSPHz/ZXTsi8S00usEV6v1tjq8tOUZzw7DpSDWVXjXDre6ed1w/pd495ODpHZYSdkRTsa0HA==",
+      "dependencies": {
+        "jwa": "^1.4.1",
+        "safe-buffer": "^5.0.1"
+      }
+    },
     "node_modules/kareem": {
       "version": "2.5.1",
       "resolved": "https://registry.npmjs.org/kareem/-/kareem-2.5.1.tgz",
@@ -868,6 +954,11 @@
         "node": ">=12.0.0"
       }
     },
+    "node_modules/lodash": {
+      "version": "4.17.21",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
+      "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg=="
+    },
     "node_modules/lodash.sortby": {
       "version": "4.7.0",
       "resolved": "https://registry.npmjs.org/lodash.sortby/-/lodash.sortby-4.7.0.tgz",
@@ -1270,6 +1361,31 @@
         "node": ">=6"
       }
     },
+    "node_modules/semver": {
+      "version": "7.5.0",
+      "resolved": "https://registry.npmjs.org/semver/-/semver-7.5.0.tgz",
+      "integrity": "sha512-+XC0AD/R7Q2mPSRuy2Id0+CGTZ98+8f+KvwirxOKIEyid+XSx6HbC63p+O4IndTHuX5Z+JxQ0TghCkO5Cg/2HA==",
+      "dependencies": {
+        "lru-cache": "^6.0.0"
+      },
+      "bin": {
+        "semver": "bin/semver.js"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
+    "node_modules/semver/node_modules/lru-cache": {
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-6.0.0.tgz",
+      "integrity": "sha512-Jo6dJ04CmSjuznwJSS3pUeWmd/H0ffTlkXXgwZi+eq1UCmqQwCh+eLsYOYCwY991i2Fah4h1BEMCx4qThGbsiA==",
+      "dependencies": {
+        "yallist": "^4.0.0"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
     "node_modules/send": {
       "version": "0.18.0",
       "resolved": "https://registry.npmjs.org/send/-/send-0.18.0.tgz",
@@ -1477,6 +1593,31 @@
         "tr46": "~0.0.3",
         "webidl-conversions": "^3.0.0"
       }
+    },
+    "node_modules/ws": {
+      "version": "8.13.0",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-8.13.0.tgz",
+      "integrity": "sha512-x9vcZYTrFPC7aSIbj7sRCYo7L/Xb8Iy+pW0ng0wt2vCJv7M9HOMy0UoN3rr+IFC7hb7vXoqS+P9ktyLLLhO+LA==",
+      "engines": {
+        "node": ">=10.0.0"
+      },
+      "peerDependencies": {
+        "bufferutil": "^4.0.1",
+        "utf-8-validate": ">=5.0.2"
+      },
+      "peerDependenciesMeta": {
+        "bufferutil": {
+          "optional": true
+        },
+        "utf-8-validate": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/yallist": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+      "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A=="
     }
   }
 }
diff --git a/apollo-graphql/server/package.json b/apollo-graphql/server/package.json
index 8a9c3e0..f4cac09 100644
--- a/apollo-graphql/server/package.json
+++ b/apollo-graphql/server/package.json
@@ -10,8 +10,15 @@
   "license": "MIT",
   "dependencies": {
     "@apollo/server": "^4.6.0",
+    "@graphql-tools/schema": "^9.0.18",
+    "cors": "^2.8.5",
     "dotenv": "^16.0.3",
+    "express": "^4.18.2",
     "graphql": "^16.6.0",
-    "mongoose": "^7.0.4"
+    "graphql-subscriptions": "^2.0.0",
+    "graphql-ws": "^5.12.1",
+    "jsonwebtoken": "^9.0.0",
+    "mongoose": "^7.0.4",
+    "ws": "^8.13.0"
   }
 }
diff --git a/apollo-graphql/server/resolvers/resolvers.js b/apollo-graphql/server/resolvers/resolvers.js
new file mode 100644
index 0000000..a9a9211
--- /dev/null
+++ b/apollo-graphql/server/resolvers/resolvers.js
@@ -0,0 +1,138 @@
+const { GraphQLError } = require('graphql');
+const jwt = require('jsonwebtoken');
+const { PubSub } = require('graphql-subscriptions');
+const pubsub = new PubSub();
+const Person = require('../models/person');
+const User = require('../models/user');
+
+const resolvers = {
+  Query: {
+    me: (root, args, context) => context.currentUser,
+    personCount: async () => Person.collection.countDocuments(),
+    allPersons: async (root, args) => {
+      if (!args.phone) {
+        return Person.find({}).populate('friendOf');
+      }
+      return Person.find({
+        phone: {
+          $exists: args.phone === 'YES'
+          }
+        }).populate('friendOf');
+    },
+    findPerson: async (root, args) =>
+      await Person.findOne({ name: args.name}).populate('friendOf')
+  },
+  Person: {
+    address: (root) => ({ street: root.street, city: root.city }),
+    friendOf: async (root) => {
+      // return list of users 
+      const friends = await User.find({
+        friends: {
+          $in: [root._id]
+        } 
+      });
+      return friends;
+    }
+  },
+  Mutation: {
+    addPerson: async (root, args, context) => {
+      const currentUser = context.currentUser;
+      if (!currentUser) {
+        throw new GraphQLError('not authenticated', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+          }
+        })
+      }
+      const person = new Person({ ...args });
+      try {
+        await person.save();
+        currentUser.friends = currentUser.friends.concat(person)
+        await currentUser.save()
+      } catch (error) {
+        throw new GraphQLError('Saving person failed', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+            invalidArgs: args.name,
+            error
+          }
+        });
+      }
+      pubsub.publish('PERSON_ADDED', { personAdded: person });
+      return person;
+    },
+    editPhone: async (root, args, context) => {
+      if (!context.currentUser) {
+        throw new GraphQLError('not authenticated', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+          }
+        });
+      }
+      const person = await Person.findOne({ name: args.name });
+      person.phone = args.phone;
+      try {
+        await person.save();
+      } catch (error) {
+        throw new GraphQLError('Saving person failed', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+            invalidArgs: args.name,
+            error
+          }
+        });
+      }
+      return person;
+    },
+    addAsFriend: async (root, args, context) => {
+      const currentUser = context.currentUser;
+      if (!currentUser) {
+        throw new GraphQLError('wrong credentials', {
+          extensions: { code: 'BAD_USER_INPUT' }
+        }) 
+      }
+
+      const person = Person.findOne({ name: args.name });
+      if (!currentUser.friends.some(f=> f._id.toString() === person._id.toString())) {
+        currentUser.friends = currentUser.friends.concat(person);
+      }
+      return await currentUser.save();
+    },
+    createUser: async (root, args) => {
+      const user = new User({ username: args.username });
+      return user.save().catch(e => {
+        throw new GraphQLError('User creation failed', {
+          extensions: {
+            code: 'BAD_USER_INPUT',
+            invalidArgs: args.name,
+            error: e
+          }
+        });
+      });
+    },
+    login: async (root, args) => {
+      const user = await User.findOne({ username: args.username });
+      // hard coded password: 'secret'
+      // change to password hash and store in user collection
+      if ( !user || args.password !== 'secret' ) {
+        throw new GraphQLError('wrong credentials', {
+          extensions: {
+            code: 'BAD_USER_INPUT'
+          }
+        })        
+      }
+      const userForToken = {
+        username: user.username,
+        id: user._id,
+      }
+      return { value: jwt.sign(userForToken, process.env.JWT_SECRET) }
+    }
+  },
+  Subscription: {
+    personAdded: {
+      subscribe: () => pubsub.asyncIterator('PERSON_ADDED')
+    },
+  },
+}
+
+module.exports = resolvers;
diff --git a/apollo-graphql/server/schemas/schemas.js b/apollo-graphql/server/schemas/schemas.js
new file mode 100644
index 0000000..1d4c147
--- /dev/null
+++ b/apollo-graphql/server/schemas/schemas.js
@@ -0,0 +1,67 @@
+const typeDefs = `
+  type Address {
+    street: String!
+    city: String!
+  }
+
+  type Person {
+    name: String!
+    phone: String
+    address: Address!
+    friendOf: [User!]!
+    id: ID!
+  }
+
+  type User {
+    username: String!
+    friends: [Person!]!
+    id: ID!
+  }
+
+  type Token {
+    value: String!
+  }
+
+  enum YesNo {
+    YES NO
+  }
+
+  type Query {
+    me: User!
+    personCount: Int!
+    allPersons(hasPhone: YesNo): [Person!]!
+    findPerson(name: String!): Person
+  }
+
+  type Mutation {
+    addPerson(
+      name: String!
+      phone: String
+      street: String!
+      city: String!
+    ): Person
+
+    editPhone(
+      name: String!
+      phone: String!
+    ): Person
+
+    addAsFriend(
+      name: String!
+    ): User
+
+    createUser(
+      username: String!
+    ): User
+
+    login(
+      username: String!
+      password: String!
+    ): Token
+  }
+
+  type Subscription {
+    personAdded: Person!
+  }  
+`
+module.exports = typeDefs;
diff --git a/apollo-graphql/server/server.js b/apollo-graphql/server/server.js
index 345bf0c..d08023a 100644
--- a/apollo-graphql/server/server.js
+++ b/apollo-graphql/server/server.js
@@ -1,12 +1,19 @@
 const config = require('./utils/config');
+const { expressMiddleware } = require('@apollo/server/express4')
+const { ApolloServerPluginDrainHttpServer } = require('@apollo/server/plugin/drainHttpServer')
+const { makeExecutableSchema } = require('@graphql-tools/schema')
+const { WebSocketServer } = require('ws')
+const { useServer } = require('graphql-ws/lib/use/ws')
+const express = require('express')
+const cors = require('cors')
+const http = require('http')
+const jwt = require('jsonwebtoken')
 const { ApolloServer } = require('@apollo/server');
-const { startStandaloneServer } = require('@apollo/server/standalone');
-const { v1: uuid } = require('uuid');
-const { GraphQLError } = require('graphql');
 const mongoose = require('mongoose');
-const Person = require('./models/person');
 const User = require('./models/user');
 const logger = require('./utils/logger');
+const typeDefs = require('./schemas/schemas');
+const resolvers = require('./resolvers/resolvers');
 
 mongoose.set('strictQuery', false);
 logger.info('connecting to mongoDB...')
@@ -19,223 +26,60 @@ mongoose.connect(config.MONGODB_URI)
     logger.error('error connecting to MongoDB:', error.message)
   });
 
-// let persons = [
-//   {
-//     name: "Arto Hellas",
-//     phone: "040-123543",
-//     street: "Tapiolankatu 5 A",
-//     city: "Espoo",
-//     id: "3d594650-3436-11e9-bc57-8b80ba54c431"
-//   },
-//   {
-//     name: "Matti Luukkainen",
-//     phone: "040-432342",
-//     street: "Malminkaari 10 A",
-//     city: "Helsinki",
-//     id: '3d599470-3436-11e9-bc57-8b80ba54c431'
-//   },
-//   {
-//     name: "Venla Ruuska",
-//     street: "Nallemäentie 22 C",
-//     city: "Helsinki",
-//     id: '3d599471-3436-11e9-bc57-8b80ba54c431'
-//   },
-// ]
+mongoose.set('debug', true);
 
-const typeDefs = `
-  type Address {
-    street: String!
-    city: String!
-  }
-
-  type Person {
-    name: String!
-    phone: String
-    address: Address! 
-    id: ID!
-  }
-
-  type User {
-    username: String!
-    friends: [Person!]!
-    id: ID!
-  }
-
-  type Token {
-    value: String!
-  }
-
-  enum YesNo {
-    YES NO
-  }
-
-  type Query {
-    personCount: Int!
-    allPersons(hasPhone: YesNo): [Person!]!
-    findPerson(name: String!): Person
-  }
-
-  type Mutation {
-    addPerson(
-      name: String!
-      phone: String
-      street: String!
-      city: String!
-    ): Person
-
-    editPhone(
-      name: String!
-      phone: String!
-    ): Person
-
-    addAsFriend(
-      name: String!
-    ): User
-
-    createUser(
-      username: String!
-    ): User
-
-    login(
-      username: String!
-      password: String!
-    ): Token
-  }
-`
-
-const resolvers = {
-  Query: {
-    me: (root, args, context) => context.currentUser,
-    personCount: async () => Person.collection.countDocuments(),
-    allPersons: async (root, args) => {
-      if (!args.phone) {
-        return Person.find({});
-      }
-      return Person.find({
-        phone: {
-          $exists: args.phone === 'YES'
-          }
-        });
-    },
-    findPerson: async (root, args) =>
-      Person.findOne({ name: args.name})
-  },
-  Person: {
-    address: (root) => ({ street: root.street, city: root.city })
-  },
-  Mutation: {
-    addPerson: async (root, args, context) => {
-      const currentUser = context.currentUser;
-      if (!currentUser) {
-        throw new GraphQLError('not authenticated', {
-          extensions: {
-            code: 'BAD_USER_INPUT',
-          }
-        })
-      }
-      const person = new Person({ ...args });
-      try {
-        await person.save();
-        currentUser.friends = currentUser.friends.concat(person)
-        await currentUser.save()
-      } catch (error) {
-        throw new GraphQLError('Saving person failed', {
-          extensions: {
-            code: 'BAD_USER_INPUT',
-            invalidArgs: args.name,
-            error
-          }
-        });
-      }
-      return person;
-    },
-    editPhone: async (root, args, context) => {
-      if (!context.currentUser) {
-        throw new GraphQLError('not authenticated', {
-          extensions: {
-            code: 'BAD_USER_INPUT',
-          }
-        });
-      }
-      const person = await Person.findOne({ name: args.name });
-      person.phone = args.phone;
-      try {
-        await person.save();
-      } catch (error) {
-        throw new GraphQLError('Saving person failed', {
-          extensions: {
-            code: 'BAD_USER_INPUT',
-            invalidArgs: args.name,
-            error
-          }
-        });
-      }
-      return person;
-    },
-    addAsFriend: async (root, args, context) => {
-      const currentUser = context.currentUser;
-      if (!currentUser) {
-        throw new GraphQLError('wrong credentials', {
-          extensions: { code: 'BAD_USER_INPUT' }
-        }) 
-      }
-
-      const person = Person.findOne({ name: args.name });
-      if (!currentUser.friends.some(f=> f._id.toString() === person._id.toString())) {
-        currentUser.friends = currentUser.friends.concat(person);
-      }
-      return await currentUser.save();
-    },
-    createUser: async (root, args) => {
-      const user = new User({ username: args.username });
-      return user.save().catch(e => {
-        throw new GraphQLError('User creation failed', {
-          extensions: {
-            code: 'BAD_USER_INPUT',
-            invalidArgs: args.name,
-            error: e
-          }
-        });
-      });
-    },
-    login: async (root, args) => {
-      const user = await User.findOne({ username: args.username });
-      // hard coded password: 'secret'
-      // change to password hash and store in user collection
-      if ( !user || args.password !== 'secret' ) {
-        throw new GraphQLError('wrong credentials', {
-          extensions: {
-            code: 'BAD_USER_INPUT'
-          }
-        })        
-      }
-      const userForToken = {
-        username: user.username,
-        id: user._id,
+const start = async () => {
+  const app = express();
+  const httpServer = http.createServer(app);
+  const wsServer = new WebSocketServer({
+    server: httpServer,
+    path: '/',
+  })
+  
+  const schema = makeExecutableSchema({ typeDefs, resolvers })
+  const serverCleanup = useServer({ schema }, wsServer)
+
+  const server = new ApolloServer({
+    schema,
+    plugins: [
+      ApolloServerPluginDrainHttpServer({ httpServer }),
+      {
+        async serverWillStart() {
+          return {
+            async drainServer() {
+              await serverCleanup.dispose();
+            },
+          };
+        }
       }
-      return { value: jwt.sign(userForToken, process.env.JWT_SECRET) }
-    }
-  }
-}
-
-const server = new ApolloServer({
-  typeDefs,
-  resolvers,
-})
+    ],
+  });
 
-startStandaloneServer(server, {
-  listen: { port: config.PORT },
-  context: async ({ req, res }) => {
-    const auth = req ? req.headers.authorization : null
-    if (auth && auth.startsWith('Bearer ')) {
-      const decodedToken = jwt.verify(
-        auth.substring(7), process.env.JWT_SECRET
-      )
-      const currentUser = await User
-        .findById(decodedToken.id).populate('friends')
-      return { currentUser }
-    }
-  },
-}).then(({ url }) => {
-  console.log(`Server ready at ${url}`)
-})
+  await server.start();
+
+  app.use(
+    '/',
+    cors(),
+    express.json(),
+    expressMiddleware(server, {
+      context: async ({ req }) => {
+        const auth = req ? req.headers.authorization : null
+        if (auth && auth.startsWith('Bearer ')) {
+          const decodedToken = jwt.verify(auth.substring(7), process.env.JWT_SECRET)
+          const currentUser = await User.findById(decodedToken.id).populate(
+            'friends'
+          )
+          return { currentUser }
+        }
+      },
+    }),
+  );
+
+  const PORT = config.PORT;
+
+  httpServer.listen(PORT, () =>
+    console.log(`Server is now running on http://localhost:${PORT}`)
+  );
+};
+
+start();