diff --git a/fitlien-services-pipeline.yaml b/fitlien-services-pipeline.yaml
new file mode 100644
index 0000000..48a4039
--- /dev/null
+++ b/fitlien-services-pipeline.yaml
@@ -0,0 +1,83 @@
+trigger:
+  - master
+
+pool:
+  vmImage: "ubuntu-latest"
+
+variables:
+  major: $(VERSION_MAJOR)
+  minor: $(VERSION_MINOR)
+  prefix: $[format('{0}.{1}', variables['major'], variables['minor'])]
+  patch: $[counter(variables['prefix'], 100)]
+  buildNumber: $(major).$(minor).$(patch)
+
+steps:
+  - task: PowerShell@2
+    displayName: "Setting build version"
+    inputs:
+      targetType: "inline"
+      script: |
+        Write-Host "##vso[build.updatebuildnumber]${{ parameters.buildNumber }}"
+
+  - task: NodeTool@0
+    displayName: "Install Node"
+    inputs:
+      version: "20"
+
+  - task: Npm@1
+    displayName: "npm install"
+    inputs:
+      command: "install"
+
+  - task: PowerShell@2
+    displayName: "Set version in package.json"
+    inputs:
+      targetType: "inline"
+      script: |
+        $pkg = Get-Content -Path "$(System.DefaultWorkingDirectory)/functions/package.json" -Raw | ConvertFrom-Json
+        $pkg.version = "${{ parameters.buildNumber }}"
+        $pkg | ConvertTo-Json -Depth 100 | Set-Content -Path "$(System.DefaultWorkingDirectory)/functions/package.json"
+
+  - task: CmdLine@2
+    displayName: "Copy .env.example to .env"
+    inputs:
+      script: |
+        cp "$(System.DefaultWorkingDirectory)/functions/.env.example" "$(System.DefaultWorkingDirectory)/functions/.env"
+
+  - task: ReplaceTokens@3
+    displayName: "Replace tokens in .env file"
+    inputs:
+      targetFiles: "$(System.DefaultWorkingDirectory)/functions/.env"
+      tokenPrefix: "#{"
+      tokenSuffix: "}#"
+
+  - task: Npm@1
+    displayName: "npm run build"
+    inputs:
+      command: "custom"
+      workingDir: "$(System.DefaultWorkingDirectory)/functions"
+      customCommand: "run build"
+
+  - task: DeleteFiles@1
+    displayName: "Remove node_modules, *.log files, src directory from functions directory"
+    inputs:
+      SourceFolder: "$(System.DefaultWorkingDirectory)/functions"
+      Contents: |
+        node_modules/**
+        *.log
+        src/**
+
+  - task: ArchiveFiles@2
+    displayName: "Archive functions directory"
+    inputs:
+      rootFolderOrFile: "$(System.DefaultWorkingDirectory)/functions"
+      includeRootFolder: false
+      archiveFile: "$(System.DefaultWorkingDirectory)/fitlien-services-$(buildNumber).zip"
+      compression: "zip"
+
+  - task: CopyFiles@2
+    displayName: "Copy archive to staging directory"
+    inputs:
+      SourceFolder: "$(System.DefaultWorkingDirectory)"
+      Contents: "fitlien-services-$(buildNumber).zip"
+      TargetFolder: "$(System.ArtifactsDirectory)"
diff --git a/functions/.env.example b/functions/.env.example
new file mode 100644
index 0000000..ed58607
--- /dev/null
+++ b/functions/.env.example
@@ -0,0 +1,6 @@
+MAILGUN_API_KEY=#{MAILGUN_API_KEY}#
+MAILGUN_SERVER=#{MAILGUN_SERVER}#
+MAILGUN_FROM_ADDRESS=#{MAILGUN_FROM_ADDRESS}#
+TWILIO_ACCOUNT_SID=AC5cfaae728ba68fb1aa6756d973b6e32b
+TWILIO_AUTH_TOKEN=886ed704c7918078f361f5f88b42ffc0
+TWILIO_PHONE_NUMBER=+12315005309
diff --git a/functions/package-lock.json b/functions/package-lock.json
index a27a770..1165bbe 100644
--- a/functions/package-lock.json
+++ b/functions/package-lock.json
@@ -1,15 +1,18 @@
 {
   "name": "functions",
+  "version": "0.0.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "functions",
+      "version": "0.0.0",
       "dependencies": {
         "firebase-admin": "^12.6.0",
         "firebase-functions": "^6.0.1",
         "form-data": "^4.0.1",
         "html-to-text": "^9.0.5",
+        "long": "4.0.0",
         "mailgun.js": "^10.4.0",
         "twilio": "^5.4.0"
       },
@@ -765,6 +768,12 @@
         "node": ">=6"
       }
     },
+    "node_modules/@grpc/proto-loader/node_modules/long": {
+      "version": "5.3.1",
+      "resolved": "https://registry.npmjs.org/long/-/long-5.3.1.tgz",
+      "integrity": "sha512-ka87Jz3gcx/I7Hal94xaN2tZEOPoUOEVftkQqZx2EeQRN7LGdfLlI3FvZ+7WDplm+vK2Urx9ULrvSowtdCieng==",
+      "optional": true
+    },
     "node_modules/@istanbuljs/load-nyc-config": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/@istanbuljs/load-nyc-config/-/load-nyc-config-1.1.0.tgz",
@@ -2743,9 +2752,9 @@
       }
     },
     "node_modules/firebase-functions": {
-      "version": "6.2.0",
-      "resolved": "https://registry.npmjs.org/firebase-functions/-/firebase-functions-6.2.0.tgz",
-      "integrity": "sha512-vfyyVHS8elxplzEQ9To+NaINRPFUsDasQrasTa2eFJBYSPzdhkw6rwLmvwyYw622+ze+g4sDIb14VZym+afqXQ==",
+      "version": "6.3.2",
+      "resolved": "https://registry.npmjs.org/firebase-functions/-/firebase-functions-6.3.2.tgz",
+      "integrity": "sha512-FC3A1/nhqt1ZzxRnj5HZLScQaozAcFSD/vSR8khqSoFNOfxuXgwJS6ZABTB7+v+iMD5z6Mmxw6OfqITUBuI7OQ==",
       "dependencies": {
         "@types/cors": "^2.8.5",
         "@types/express": "^4.17.21",
@@ -4425,9 +4434,9 @@
       "integrity": "sha512-Sb487aTOCr9drQVL8pIxOzVhafOjZN9UU54hiN8PU3uAiSV7lx1yYNpbNmex2PK6dSJoNTSJUUswT651yww3Mg=="
     },
     "node_modules/long": {
-      "version": "5.2.3",
-      "resolved": "https://registry.npmjs.org/long/-/long-5.2.3.tgz",
-      "integrity": "sha512-lcHwpNoggQTObv5apGNCTdJrO69eHOZMi4BNC+rTLER8iHAqGrUVeLh/irVIM7zTw2bOXA8T6uNPeujwOLg/2Q=="
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/long/-/long-4.0.0.tgz",
+      "integrity": "sha512-XsP+KhQif4bjX1kbuSiySJFNAehNxgLb6hPRGJ9QsUr8ajHkuXGdrHmFUTUUXhDwVX2R5bY4JNZEwbUiMhV+MA=="
     },
     "node_modules/lru-cache": {
       "version": "5.1.1",
@@ -5035,6 +5044,11 @@
         "node": ">=12.0.0"
       }
     },
+    "node_modules/protobufjs/node_modules/long": {
+      "version": "5.3.1",
+      "resolved": "https://registry.npmjs.org/long/-/long-5.3.1.tgz",
+      "integrity": "sha512-ka87Jz3gcx/I7Hal94xaN2tZEOPoUOEVftkQqZx2EeQRN7LGdfLlI3FvZ+7WDplm+vK2Urx9ULrvSowtdCieng=="
+    },
     "node_modules/proxy-addr": {
       "version": "2.0.7",
       "resolved": "https://registry.npmjs.org/proxy-addr/-/proxy-addr-2.0.7.tgz",
diff --git a/functions/package.json b/functions/package.json
index 75380f3..6ad5eae 100644
--- a/functions/package.json
+++ b/functions/package.json
@@ -1,5 +1,6 @@
 {
   "name": "functions",
+  "version": "0.0.0",
   "scripts": {
     "build": "tsc",
     "build:watch": "tsc --watch",
@@ -18,6 +19,7 @@
     "firebase-functions": "^6.0.1",
     "form-data": "^4.0.1",
     "html-to-text": "^9.0.5",
+    "long": "4.0.0",
     "mailgun.js": "^10.4.0",
     "twilio": "^5.4.0"
   },
diff --git a/functions/src/index.ts b/functions/src/index.ts
index 48594d4..3a9f80c 100644
--- a/functions/src/index.ts
+++ b/functions/src/index.ts
@@ -1,11 +1,16 @@
 import { onRequest } from "firebase-functions/v2/https";
+import { Request } from "firebase-functions/v2/https";
+import { onDocumentCreated } from 'firebase-functions/v2/firestore';
+import * as admin from 'firebase-admin';
+import * as express from "express";
 import * as logger from "firebase-functions/logger";
+
 const formData = require('form-data');
 const Mailgun = require('mailgun.js');
 const { convert } = require('html-to-text');
 const twilio = require('twilio')
 
-export const sendEmail = onRequest((request, response) => {
+export const sendEmail = onRequest((request: Request, response: express.Response) => {
     const mailgun = new Mailgun(formData);
     const mailGunClient = mailgun.client({ username: 'api', key: process.env.MAILGUN_API_KEY });
 
@@ -32,11 +37,9 @@ export const sendEmail = onRequest((request, response) => {
     });
 });
 
-export const sendSMS = onRequest((request, response) => {
+export const sendSMS = onRequest((request: Request, response: express.Response) => {
     const client = twilio(process.env.TWILIO_ACCOUNT_SID, process.env.TWILIO_AUTH_TOKEN);
-    
     const { to, body } = request.body;
-    
     client.messages
         .create({
             body: body,
@@ -52,3 +55,81 @@ export const sendSMS = onRequest((request, response) => {
             response.status(500).json({ success: false, error: error.message });
         });
 });
+
+
+interface Invitation {
+  email: string;
+  phoneNumber: string;
+  gymName: string;
+  invitedByName: string;
+}
+
+export const sendInvitationNotification = onDocumentCreated(
+  'invitations/{invitationId}',
+  async (event) => {
+    const invitation = event.data?.data() as Invitation;
+    const invitationId = event.params.invitationId;
+
+    if (!invitation) {
+      console.error('Invitation data is missing.');
+      return null;
+    }
+
+    try {
+      const userQuery = await admin
+        .firestore()
+        .collection('users')
+        .where('email', '==', invitation.email)
+        .where('phoneNumber', '==', invitation.phoneNumber)
+        .limit(1)
+        .get();
+
+      if (userQuery.empty) {
+        console.log(
+          `User not found for email: ${invitation.email} and phone: ${invitation.phoneNumber}.`
+        );
+        return null;
+      }
+
+      const user = userQuery.docs[0].data();
+      const fcmToken = user.fcmToken;
+
+      if (!fcmToken) {
+        console.log(`FCM token not found for user: ${invitation.email}.`);
+        return null;
+      }
+
+      const message: admin.messaging.Message = {
+        notification: {
+          title: 'New Gym Invitation',
+          body: `${invitation.invitedByName} has invited you to join ${invitation.gymName}`,
+        },
+        data: {
+          type: 'invitation',
+          invitationId: invitationId,
+          gymName: invitation.gymName,
+          senderName: invitation.invitedByName,
+        },
+        android: {
+          priority: 'high',
+          notification: {
+            channelId: 'invitations_channel',
+            priority: 'high',
+            defaultSound: true,
+            defaultVibrateTimings: true,
+            icon: '@mipmap/ic_launcher',
+            clickAction: 'FLUTTER_NOTIFICATION_CLICK',
+          },
+        },
+        token: fcmToken,
+      };
+
+      await admin.messaging().send(message);
+      console.log(`Invitation notification sent to ${invitation.email}.`);
+      return null;
+    } catch (error) {
+      console.error('Error sending invitation notification:', error);
+      return null;
+    }
+  }
+);
\ No newline at end of file
diff --git a/functions/tsconfig.json b/functions/tsconfig.json
index 57b915f..2924892 100644
--- a/functions/tsconfig.json
+++ b/functions/tsconfig.json
@@ -2,7 +2,8 @@
   "compilerOptions": {
     "module": "NodeNext",
     "esModuleInterop": true,
-    "moduleResolution": "nodenext",
+    "allowSyntheticDefaultImports": true,
+    "moduleResolution": "node16",
     "noImplicitReturns": true,
     "noUnusedLocals": true,
     "outDir": "lib",