diff --git a/.env b/.env
new file mode 100644
index 0000000..48c9ad9
--- /dev/null
+++ b/.env
@@ -0,0 +1,5 @@
+NODE_PORT=3001
+MONGO_PORT=27017
+MONGO_CONN_STRING=""
+MONGO_NAME=""
+COLLECTION_NAME=""
\ No newline at end of file
diff --git a/.prettierrc b/.prettierrc
index 0967ef4..8db60ca 100644
--- a/.prettierrc
+++ b/.prettierrc
@@ -1 +1,3 @@
-{}
+{
+    "singleQuote": true
+}
diff --git a/compose.yml b/compose.yml
index b54e53d..b87aa0a 100644
--- a/compose.yml
+++ b/compose.yml
@@ -3,17 +3,31 @@ services:
     container_name: ts-catservice-docker
     restart: always
     ports: 
-      - 3001:${PORT}
+      - 3001:${NODE_PORT}
     env_file:
       - .env
     build: 
       context: .
       target: production
       args: 
-        - PORT=${PORT}
+        - PORT=${NODE_PORT}
     volumes: 
       - volume:/usr/src/app
       - ignore:/usr/src/app/node_modules/
+    networks:
+      - catservice-network
+    depends_on:
+      - mongo-database
+  mongo-database:
+    container_name: mongo-database
+    image: mongo
+    ports:
+      - 27017:${MONGO_PORT}
+    networks:
+      - catservice-network
+networks:
+  catservice-network:
+    driver: bridge
 volumes: 
   ignore:
   volume:
diff --git a/eslint.config.js b/eslint.config.js
index 4035671..149ac8f 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -14,6 +14,7 @@ export default defineConfig([
   { files: ["**/*.md"], plugins: { markdown }, language: "markdown/gfm", extends: ["markdown/recommended"] },
   { rules: {
     ...tseslint.configs.recommended.rules,
-    "no-explicit-any": "warn"
+    "no-explicit-any": "warn",
+    "quotes": ["error", "single"]
   }}
 ]);
diff --git a/package-lock.json b/package-lock.json
index 87c56d2..70f36ef 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14,6 +14,7 @@
                 "cors": "^2.8.5",
                 "express": "^4.16.1",
                 "jsonschema": "^1.4.1",
+                "mongodb": "^6.17.0",
                 "uuid": "^9.0.0"
             },
             "devDependencies": {
@@ -1416,6 +1417,15 @@
                 "@jridgewell/sourcemap-codec": "^1.4.10"
             }
         },
+        "node_modules/@mongodb-js/saslprep": {
+            "version": "1.3.0",
+            "resolved": "https://registry.npmjs.org/@mongodb-js/saslprep/-/saslprep-1.3.0.tgz",
+            "integrity": "sha512-zlayKCsIjYb7/IdfqxorK5+xUMyi4vOKcFy10wKJYc63NSdKI8mNME+uJqfatkPmOSMMUiojrL58IePKBm3gvQ==",
+            "license": "MIT",
+            "dependencies": {
+                "sparse-bitfield": "^3.0.3"
+            }
+        },
         "node_modules/@nodelib/fs.scandir": {
             "version": "2.1.5",
             "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",
@@ -1769,6 +1779,21 @@
             "dev": true,
             "license": "MIT"
         },
+        "node_modules/@types/webidl-conversions": {
+            "version": "7.0.3",
+            "resolved": "https://registry.npmjs.org/@types/webidl-conversions/-/webidl-conversions-7.0.3.tgz",
+            "integrity": "sha512-CiJJvcRtIgzadHCYXw7dqEnMNRjhGZlYK05Mj9OyktqV8uVT8fD2BFOB7S1uwBE3Kj2Z+4UyPmFw/Ixgw/LAlA==",
+            "license": "MIT"
+        },
+        "node_modules/@types/whatwg-url": {
+            "version": "11.0.5",
+            "resolved": "https://registry.npmjs.org/@types/whatwg-url/-/whatwg-url-11.0.5.tgz",
+            "integrity": "sha512-coYR071JRaHa+xoEvvYqvnIHaVqaYrLPbsufM9BF63HkwI5Lgmy2QR8Q5K/lYDYo5AK82wOvSOS0UsLTpTG7uQ==",
+            "license": "MIT",
+            "dependencies": {
+                "@types/webidl-conversions": "*"
+            }
+        },
         "node_modules/@types/yargs": {
             "version": "17.0.12",
             "resolved": "https://registry.npmjs.org/@types/yargs/-/yargs-17.0.12.tgz",
@@ -2529,6 +2554,15 @@
                 "node-int64": "^0.4.0"
             }
         },
+        "node_modules/bson": {
+            "version": "6.10.4",
+            "resolved": "https://registry.npmjs.org/bson/-/bson-6.10.4.tgz",
+            "integrity": "sha512-WIsKqkSC0ABoBJuT1LEX+2HEvNmNKKgnTAyd0fL8qzK4SH2i9NXg+t08YtdZp/V9IZ33cxe3iV4yM0qg8lMQng==",
+            "license": "Apache-2.0",
+            "engines": {
+                "node": ">=16.20.1"
+            }
+        },
         "node_modules/buffer-from": {
             "version": "1.1.2",
             "resolved": "https://registry.npmjs.org/buffer-from/-/buffer-from-1.1.2.tgz",
@@ -5148,6 +5182,12 @@
                 "node": ">= 0.6"
             }
         },
+        "node_modules/memory-pager": {
+            "version": "1.5.0",
+            "resolved": "https://registry.npmjs.org/memory-pager/-/memory-pager-1.5.0.tgz",
+            "integrity": "sha512-ZS4Bp4r/Zoeq6+NLJpP+0Zzm0pR8whtGPf1XExKLJBAczGMnSi3It14OiNCStjQjM6NU1okjQGSxgEZN8eBYKg==",
+            "license": "MIT"
+        },
         "node_modules/merge-descriptors": {
             "version": "1.0.1",
             "resolved": "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.1.tgz",
@@ -5871,6 +5911,62 @@
                 "node": "*"
             }
         },
+        "node_modules/mongodb": {
+            "version": "6.17.0",
+            "resolved": "https://registry.npmjs.org/mongodb/-/mongodb-6.17.0.tgz",
+            "integrity": "sha512-neerUzg/8U26cgruLysKEjJvoNSXhyID3RvzvdcpsIi2COYM3FS3o9nlH7fxFtefTb942dX3W9i37oPfCVj4wA==",
+            "license": "Apache-2.0",
+            "dependencies": {
+                "@mongodb-js/saslprep": "^1.1.9",
+                "bson": "^6.10.4",
+                "mongodb-connection-string-url": "^3.0.0"
+            },
+            "engines": {
+                "node": ">=16.20.1"
+            },
+            "peerDependencies": {
+                "@aws-sdk/credential-providers": "^3.188.0",
+                "@mongodb-js/zstd": "^1.1.0 || ^2.0.0",
+                "gcp-metadata": "^5.2.0",
+                "kerberos": "^2.0.1",
+                "mongodb-client-encryption": ">=6.0.0 <7",
+                "snappy": "^7.2.2",
+                "socks": "^2.7.1"
+            },
+            "peerDependenciesMeta": {
+                "@aws-sdk/credential-providers": {
+                    "optional": true
+                },
+                "@mongodb-js/zstd": {
+                    "optional": true
+                },
+                "gcp-metadata": {
+                    "optional": true
+                },
+                "kerberos": {
+                    "optional": true
+                },
+                "mongodb-client-encryption": {
+                    "optional": true
+                },
+                "snappy": {
+                    "optional": true
+                },
+                "socks": {
+                    "optional": true
+                }
+            }
+        },
+        "node_modules/mongodb-connection-string-url": {
+            "version": "3.0.2",
+            "resolved": "https://registry.npmjs.org/mongodb-connection-string-url/-/mongodb-connection-string-url-3.0.2.tgz",
+            "integrity": "sha512-rMO7CGo/9BFwyZABcKAWL8UJwH/Kc2x0g72uhDWzG48URRax5TCIcJ7Rc3RZqffZzO/Gwff/jyKwCU9TN8gehA==",
+            "license": "Apache-2.0",
+            "dependencies": {
+                "@types/whatwg-url": "^11.0.2",
+                "whatwg-url": "^14.1.0 || ^13.0.0"
+            }
+        },
         "node_modules/ms": {
             "version": "2.0.0",
             "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
@@ -6320,7 +6416,6 @@
             "version": "2.3.1",
             "resolved": "https://registry.npmjs.org/punycode/-/punycode-2.3.1.tgz",
             "integrity": "sha512-vYt7UD1U9Wg6138shLtLOvdAu+8DsC/ilFtEVHcH+wydcSpNE20AfSOduf6MkRFahL5FY7X1oU7nKVZFtfq8Fg==",
-            "dev": true,
             "license": "MIT",
             "engines": {
                 "node": ">=6"
@@ -6661,6 +6756,15 @@
                 "source-map": "^0.6.0"
             }
         },
+        "node_modules/sparse-bitfield": {
+            "version": "3.0.3",
+            "resolved": "https://registry.npmjs.org/sparse-bitfield/-/sparse-bitfield-3.0.3.tgz",
+            "integrity": "sha512-kvzhi7vqKTfkh0PZU+2D2PIllw2ymqJKujUcyPMd9Y75Nv4nPbGJZXNhxsgdQab2BmlDct1YnfQCguEvHr7VsQ==",
+            "license": "MIT",
+            "dependencies": {
+                "memory-pager": "^1.0.2"
+            }
+        },
         "node_modules/sprintf-js": {
             "version": "1.0.3",
             "resolved": "https://registry.npmjs.org/sprintf-js/-/sprintf-js-1.0.3.tgz",
@@ -6891,6 +6995,18 @@
                 "nodetouch": "bin/nodetouch.js"
             }
         },
+        "node_modules/tr46": {
+            "version": "5.1.1",
+            "resolved": "https://registry.npmjs.org/tr46/-/tr46-5.1.1.tgz",
+            "integrity": "sha512-hdF5ZgjTqgAntKkklYw0R03MG2x/bSzTtkxmIRw/sTNV8YXsCJ1tfLAX23lhxhHJlEf3CRCOCGGWw3vI3GaSPw==",
+            "license": "MIT",
+            "dependencies": {
+                "punycode": "^2.3.1"
+            },
+            "engines": {
+                "node": ">=18"
+            }
+        },
         "node_modules/ts-api-utils": {
             "version": "2.1.0",
             "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-2.1.0.tgz",
@@ -7206,6 +7322,28 @@
                 "makeerror": "1.0.12"
             }
         },
+        "node_modules/webidl-conversions": {
+            "version": "7.0.0",
+            "resolved": "https://registry.npmjs.org/webidl-conversions/-/webidl-conversions-7.0.0.tgz",
+            "integrity": "sha512-VwddBukDzu71offAQR975unBIGqfKZpM+8ZX6ySk8nYhVoo5CYaZyzt3YBvYtRtO+aoGlqxPg/B87NGVZ/fu6g==",
+            "license": "BSD-2-Clause",
+            "engines": {
+                "node": ">=12"
+            }
+        },
+        "node_modules/whatwg-url": {
+            "version": "14.2.0",
+            "resolved": "https://registry.npmjs.org/whatwg-url/-/whatwg-url-14.2.0.tgz",
+            "integrity": "sha512-De72GdQZzNTUBBChsXueQUnPKDkg/5A5zp7pFDuQAj5UFoENpiACU0wlCvzpAGnTkj++ihpKwKyYewn/XNUbKw==",
+            "license": "MIT",
+            "dependencies": {
+                "tr46": "^5.1.0",
+                "webidl-conversions": "^7.0.0"
+            },
+            "engines": {
+                "node": ">=18"
+            }
+        },
         "node_modules/which": {
             "version": "2.0.2",
             "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
@@ -8359,6 +8497,14 @@
                 "@jridgewell/sourcemap-codec": "^1.4.10"
             }
         },
+        "@mongodb-js/saslprep": {
+            "version": "1.3.0",
+            "resolved": "https://registry.npmjs.org/@mongodb-js/saslprep/-/saslprep-1.3.0.tgz",
+            "integrity": "sha512-zlayKCsIjYb7/IdfqxorK5+xUMyi4vOKcFy10wKJYc63NSdKI8mNME+uJqfatkPmOSMMUiojrL58IePKBm3gvQ==",
+            "requires": {
+                "sparse-bitfield": "^3.0.3"
+            }
+        },
         "@nodelib/fs.scandir": {
             "version": "2.1.5",
             "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",
@@ -8679,6 +8825,19 @@
             "integrity": "sha512-7gqG38EyHgyP1S+7+xomFtL+ZNHcKv6DwNaCZmJmo1vgMugyF3TCnXVg4t1uk89mLNwnLtnY3TpOpCOyp1/xHQ==",
             "dev": true
         },
+        "@types/webidl-conversions": {
+            "version": "7.0.3",
+            "resolved": "https://registry.npmjs.org/@types/webidl-conversions/-/webidl-conversions-7.0.3.tgz",
+            "integrity": "sha512-CiJJvcRtIgzadHCYXw7dqEnMNRjhGZlYK05Mj9OyktqV8uVT8fD2BFOB7S1uwBE3Kj2Z+4UyPmFw/Ixgw/LAlA=="
+        },
+        "@types/whatwg-url": {
+            "version": "11.0.5",
+            "resolved": "https://registry.npmjs.org/@types/whatwg-url/-/whatwg-url-11.0.5.tgz",
+            "integrity": "sha512-coYR071JRaHa+xoEvvYqvnIHaVqaYrLPbsufM9BF63HkwI5Lgmy2QR8Q5K/lYDYo5AK82wOvSOS0UsLTpTG7uQ==",
+            "requires": {
+                "@types/webidl-conversions": "*"
+            }
+        },
         "@types/yargs": {
             "version": "17.0.12",
             "resolved": "https://registry.npmjs.org/@types/yargs/-/yargs-17.0.12.tgz",
@@ -9185,6 +9344,11 @@
                 "node-int64": "^0.4.0"
             }
         },
+        "bson": {
+            "version": "6.10.4",
+            "resolved": "https://registry.npmjs.org/bson/-/bson-6.10.4.tgz",
+            "integrity": "sha512-WIsKqkSC0ABoBJuT1LEX+2HEvNmNKKgnTAyd0fL8qzK4SH2i9NXg+t08YtdZp/V9IZ33cxe3iV4yM0qg8lMQng=="
+        },
         "buffer-from": {
             "version": "1.1.2",
             "resolved": "https://registry.npmjs.org/buffer-from/-/buffer-from-1.1.2.tgz",
@@ -11098,6 +11262,11 @@
             "resolved": "https://registry.npmjs.org/media-typer/-/media-typer-0.3.0.tgz",
             "integrity": "sha512-dq+qelQ9akHpcOl/gUVRTxVIOkAJ1wR3QAvb4RsVjS8oVoFjDGTc679wJYmUmknUF5HwMLOgb5O+a3KxfWapPQ=="
         },
+        "memory-pager": {
+            "version": "1.5.0",
+            "resolved": "https://registry.npmjs.org/memory-pager/-/memory-pager-1.5.0.tgz",
+            "integrity": "sha512-ZS4Bp4r/Zoeq6+NLJpP+0Zzm0pR8whtGPf1XExKLJBAczGMnSi3It14OiNCStjQjM6NU1okjQGSxgEZN8eBYKg=="
+        },
         "merge-descriptors": {
             "version": "1.0.1",
             "resolved": "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.1.tgz",
@@ -11514,6 +11683,25 @@
                 "brace-expansion": "^1.1.7"
             }
         },
+        "mongodb": {
+            "version": "6.17.0",
+            "resolved": "https://registry.npmjs.org/mongodb/-/mongodb-6.17.0.tgz",
+            "integrity": "sha512-neerUzg/8U26cgruLysKEjJvoNSXhyID3RvzvdcpsIi2COYM3FS3o9nlH7fxFtefTb942dX3W9i37oPfCVj4wA==",
+            "requires": {
+                "@mongodb-js/saslprep": "^1.1.9",
+                "bson": "^6.10.4",
+                "mongodb-connection-string-url": "^3.0.0"
+            }
+        },
+        "mongodb-connection-string-url": {
+            "version": "3.0.2",
+            "resolved": "https://registry.npmjs.org/mongodb-connection-string-url/-/mongodb-connection-string-url-3.0.2.tgz",
+            "integrity": "sha512-rMO7CGo/9BFwyZABcKAWL8UJwH/Kc2x0g72uhDWzG48URRax5TCIcJ7Rc3RZqffZzO/Gwff/jyKwCU9TN8gehA==",
+            "requires": {
+                "@types/whatwg-url": "^11.0.2",
+                "whatwg-url": "^14.1.0 || ^13.0.0"
+            }
+        },
         "ms": {
             "version": "2.0.0",
             "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
@@ -11842,8 +12030,7 @@
         "punycode": {
             "version": "2.3.1",
             "resolved": "https://registry.npmjs.org/punycode/-/punycode-2.3.1.tgz",
-            "integrity": "sha512-vYt7UD1U9Wg6138shLtLOvdAu+8DsC/ilFtEVHcH+wydcSpNE20AfSOduf6MkRFahL5FY7X1oU7nKVZFtfq8Fg==",
-            "dev": true
+            "integrity": "sha512-vYt7UD1U9Wg6138shLtLOvdAu+8DsC/ilFtEVHcH+wydcSpNE20AfSOduf6MkRFahL5FY7X1oU7nKVZFtfq8Fg=="
         },
         "qs": {
             "version": "6.10.3",
@@ -12075,6 +12262,14 @@
                 "source-map": "^0.6.0"
             }
         },
+        "sparse-bitfield": {
+            "version": "3.0.3",
+            "resolved": "https://registry.npmjs.org/sparse-bitfield/-/sparse-bitfield-3.0.3.tgz",
+            "integrity": "sha512-kvzhi7vqKTfkh0PZU+2D2PIllw2ymqJKujUcyPMd9Y75Nv4nPbGJZXNhxsgdQab2BmlDct1YnfQCguEvHr7VsQ==",
+            "requires": {
+                "memory-pager": "^1.0.2"
+            }
+        },
         "sprintf-js": {
             "version": "1.0.3",
             "resolved": "https://registry.npmjs.org/sprintf-js/-/sprintf-js-1.0.3.tgz",
@@ -12240,6 +12435,14 @@
                 "nopt": "~1.0.10"
             }
         },
+        "tr46": {
+            "version": "5.1.1",
+            "resolved": "https://registry.npmjs.org/tr46/-/tr46-5.1.1.tgz",
+            "integrity": "sha512-hdF5ZgjTqgAntKkklYw0R03MG2x/bSzTtkxmIRw/sTNV8YXsCJ1tfLAX23lhxhHJlEf3CRCOCGGWw3vI3GaSPw==",
+            "requires": {
+                "punycode": "^2.3.1"
+            }
+        },
         "ts-api-utils": {
             "version": "2.1.0",
             "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-2.1.0.tgz",
@@ -12436,6 +12639,20 @@
                 "makeerror": "1.0.12"
             }
         },
+        "webidl-conversions": {
+            "version": "7.0.0",
+            "resolved": "https://registry.npmjs.org/webidl-conversions/-/webidl-conversions-7.0.0.tgz",
+            "integrity": "sha512-VwddBukDzu71offAQR975unBIGqfKZpM+8ZX6ySk8nYhVoo5CYaZyzt3YBvYtRtO+aoGlqxPg/B87NGVZ/fu6g=="
+        },
+        "whatwg-url": {
+            "version": "14.2.0",
+            "resolved": "https://registry.npmjs.org/whatwg-url/-/whatwg-url-14.2.0.tgz",
+            "integrity": "sha512-De72GdQZzNTUBBChsXueQUnPKDkg/5A5zp7pFDuQAj5UFoENpiACU0wlCvzpAGnTkj++ihpKwKyYewn/XNUbKw==",
+            "requires": {
+                "tr46": "^5.1.0",
+                "webidl-conversions": "^7.0.0"
+            }
+        },
         "which": {
             "version": "2.0.2",
             "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
diff --git a/package.json b/package.json
index dbbfb6c..4e80216 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,7 @@
         "cors": "^2.8.5",
         "express": "^4.16.1",
         "jsonschema": "^1.4.1",
+        "mongodb": "^6.17.0",
         "uuid": "^9.0.0"
     },
     "devDependencies": {
diff --git a/src/app/index.ts b/src/app/index.ts
index a6e9b85..25ce860 100644
--- a/src/app/index.ts
+++ b/src/app/index.ts
@@ -1,11 +1,11 @@
-import express from "express";
-import cors from "cors";
-import bodyParser from "body-parser";
-import { catRoutes } from "./v3/routes/catRoutes.js";
+import express from 'express';
+import cors from 'cors';
+import bodyParser from 'body-parser';
+import { catRoutes } from './v3/routes/catRoutes.js';
 
 const PORT = process.env.PORT || 3001;
 const corsOptions = {
-  origin: "*",
+  origin: '*',
 };
 
 const app = express();
@@ -14,6 +14,6 @@ app.use(bodyParser.json());
 app.use(cors(corsOptions));
 
 // V3 -> TypeScript and Express approach
-app.use("/api/v3/cats", catRoutes());
+app.use('/api/v3/cats', catRoutes());
 
 app.listen(PORT);
diff --git a/src/app/v3/data/Cat.ts b/src/app/v3/data/Cat.ts
index 0af3897..aea6c3d 100644
--- a/src/app/v3/data/Cat.ts
+++ b/src/app/v3/data/Cat.ts
@@ -1,5 +1,5 @@
-import { getDatabase, saveToDatabase } from "./utils.js";
-import type { SearchParams, Cat, StoredCat } from "../shared/types.js";
+import { getDatabase, saveToDatabase } from './utils.js';
+import type { SearchParams, Cat, StoredCat } from '../shared/types.js';
 
 export const getAll = (params: SearchParams) => {
   try {
@@ -93,7 +93,7 @@ export const update = (catId: string, cat: StoredCat) => {
     const updatedCat = {
       ...DB.Cats[indexForUpdate],
       ...cat,
-      updatedAt: new Date().toLocaleString("en-US", { timeZone: "UTC" }),
+      updatedAt: new Date().toLocaleString('en-US', { timeZone: 'UTC' }),
     };
     DB.Cats[indexForUpdate] = updatedCat;
     saveToDatabase(DB);
diff --git a/src/app/v3/data/CatRouter.ts b/src/app/v3/data/CatRouter.ts
new file mode 100644
index 0000000..7e133fa
--- /dev/null
+++ b/src/app/v3/data/CatRouter.ts
@@ -0,0 +1,119 @@
+import { getDatabase, saveToDatabase } from './utils.js';
+import type { SearchParams, Cat, StoredCat } from '../shared/types.js';
+import { ObjectId } from 'mongodb';
+import { collections } from './DBService.js';
+import MongoCat from './MongoCat.js';
+
+export const getAll = async (params: SearchParams) => {
+  try {
+    // Optional params to filter cats based on colorType and favoriteMeal
+    const { colorType, favoriteMeal } = params;
+    const cats = (await collections.cats
+      ?.find({
+        ...(colorType && {
+          colorType: { $eq: params.colorType?.toLowerCase() },
+        }),
+        ...(favoriteMeal && {
+          favoriteMeals: {
+            $elemMatch: { $eq: params.favoriteMeal?.toLowerCase() },
+          },
+        }),
+      })
+      .toArray()) satisfies MongoCat[] | undefined;
+
+    return {
+      cats: cats ?? [],
+    };
+  } catch (error) {
+    throw { status: 500, message: error };
+  }
+};
+
+export const get = async (catId: string) => {
+  try {
+    const cat = await collections.cats?.findOne({
+      _id: new ObjectId(catId),
+    });
+    if (!cat) {
+      throw {
+        status: 400,
+        message: `Can't find a cat with the id '${catId}'`,
+      };
+    }
+    return cat;
+  } catch (error: any) {
+    throw { status: error?.status || 500, message: error?.message || error };
+  }
+};
+
+export const add = async (newCat: Cat) => {
+  try {
+    const sameNameCat = (await collections.cats?.findOne({
+      firstName: { $eq: newCat.firstName },
+      lastName: { $eq: newCat.lastName },
+    })) satisfies MongoCat | null | undefined;
+
+    if (sameNameCat) {
+      throw {
+        status: 400,
+        message: `Cat with name ${newCat.firstName} ${newCat.lastName} already exists`,
+      };
+    }
+
+    const result = await collections.cats?.insertOne(newCat as MongoCat);
+    return result;
+  } catch (error: any) {
+    throw {
+      status: 500,
+      message: error?.message || error,
+    };
+  }
+};
+
+export const update = (catId: string, cat: StoredCat) => {
+  try {
+    const DB = getDatabase();
+    const indexForUpdate = DB.Cats.findIndex(
+      (cat: StoredCat) => cat.id === catId,
+    );
+    if (indexForUpdate === -1) {
+      throw {
+        status: 400,
+        message: `Can't find cat with id '${catId}'`,
+      };
+    }
+    const updatedCat = {
+      ...DB.Cats[indexForUpdate],
+      ...cat,
+      updatedAt: new Date().toLocaleString('en-US', { timeZone: 'UTC' }),
+    };
+    DB.Cats[indexForUpdate] = updatedCat;
+    saveToDatabase(DB);
+    return updatedCat;
+  } catch (error: any) {
+    throw {
+      status: error?.status || 500,
+      message: error?.message || error,
+    };
+  }
+};
+
+export const remove = (catId: string) => {
+  try {
+    const DB = getDatabase();
+    const indexForDeletion = DB.Cats.findIndex(
+      (cat: StoredCat) => cat.id === catId,
+    );
+    if (indexForDeletion === -1) {
+      throw {
+        status: 400,
+        message: `Can't find cat with the id '${catId}'`,
+      };
+    }
+
+    DB.Cats.splice(indexForDeletion, 1);
+    saveToDatabase(DB);
+  } catch (error: any) {
+    throw { status: error?.status || 500, message: error?.message || error };
+  }
+};
diff --git a/src/app/v3/data/DBService.ts b/src/app/v3/data/DBService.ts
new file mode 100644
index 0000000..4e66e4a
--- /dev/null
+++ b/src/app/v3/data/DBService.ts
@@ -0,0 +1,20 @@
+import * as mongoDB from 'mongodb';
+import type MongoCat from './MongoCat.js';
+
+export const collections: { cats?: mongoDB.Collection<MongoCat> } = {};
+
+export async function connectToDatabase() {
+  const { DB_CONN_STRING, DB_NAME, CATS_COLLECTION_NAME } = process.env;
+  if (!DB_CONN_STRING || !DB_NAME || !CATS_COLLECTION_NAME) {
+    throw new Error('Missing environment variables');
+  }
+
+  const client: mongoDB.MongoClient = new mongoDB.MongoClient(DB_CONN_STRING);
+
+  await client.connect();
+  const db: mongoDB.Db = client.db(DB_NAME);
+
+  const catsCollection: mongoDB.Collection<MongoCat> =
+    db.collection(CATS_COLLECTION_NAME);
+  collections.cats = catsCollection;
+}
diff --git a/src/app/v3/data/MongoCat.ts b/src/app/v3/data/MongoCat.ts
new file mode 100644
index 0000000..092cc5e
--- /dev/null
+++ b/src/app/v3/data/MongoCat.ts
@@ -0,0 +1,14 @@
+import { ObjectId } from 'mongodb';
+
+export default class MongoCat {
+  constructor(
+    public firstName: string,
+    public lastName: string,
+    public colorType: string,
+    public age: number,
+    public nicknames?: string[],
+    public favoriteMeals?: string[],
+    public externalId?: string,
+    public id?: ObjectId,
+  ) {}
+}
diff --git a/src/app/v3/data/utils.js b/src/app/v3/data/utils.js
index a765816..2a054e9 100644
--- a/src/app/v3/data/utils.js
+++ b/src/app/v3/data/utils.js
@@ -1,14 +1,14 @@
-import fs from "fs";
+import fs from 'fs';
 
 export const saveToDatabase = (/** @type {any} */ DB) => {
-  fs.writeFileSync("./src/app/v1/data/db.json", JSON.stringify(DB, null, 2), {
-    encoding: "utf-8",
+  fs.writeFileSync('./src/app/v1/data/db.json', JSON.stringify(DB, null, 2), {
+    encoding: 'utf-8',
   });
 };
 
 export const getDatabase = () => {
   const DB = JSON.parse(
-    fs.readFileSync("./src/app/v1/data/db.json").toString(),
+    fs.readFileSync('./src/app/v1/data/db.json').toString(),
   );
   return DB;
 };
diff --git a/src/app/v3/routes/catRoutes.js b/src/app/v3/routes/catRoutes.js
index b6d4983..8a501c2 100644
--- a/src/app/v3/routes/catRoutes.js
+++ b/src/app/v3/routes/catRoutes.js
@@ -1,17 +1,17 @@
-import express from "express";
-import * as catController from "../controllers/catController.js";
+import express from 'express';
+import * as catController from '../controllers/catController.js';
 
 export const catRoutes = () => {
   const router = express.Router();
-  router.get("/", catController.getAllCats);
+  router.get('/', catController.getAllCats);
 
-  router.get("/:catId", catController.getCat);
+  router.get('/:catId', catController.getCat);
 
-  router.post("/", catController.createCat);
+  router.post('/', catController.createCat);
 
-  router.patch("/:catId", catController.updateCat);
+  router.patch('/:catId', catController.updateCat);
 
-  router.delete("/:catId", catController.deleteCat);
+  router.delete('/:catId', catController.deleteCat);
 
   return router;
 };
diff --git a/src/app/v3/schemas/catSchema.js b/src/app/v3/schemas/catSchema.js
deleted file mode 100644
index 525d8b8..0000000
--- a/src/app/v3/schemas/catSchema.js
+++ /dev/null
@@ -1,37 +0,0 @@
-const catSchema = {
-  id: "/Cat",
-  type: "object",
-  properties: {
-    firstName: {
-      type: "string",
-      description: "First name of cat",
-    },
-    lastName: {
-      type: "string",
-      description: "Last name of cat",
-    },
-    colorType: {
-      type: "string",
-      description: "Brief description about the cat color type",
-    },
-    age: {
-      type: "integer",
-      description: "A numeric int representing the age of the cat",
-    },
-    nicknames: {
-      type: "array",
-      items: {
-        type: "string",
-      },
-    },
-    favoriteMeals: {
-      type: "array",
-      items: {
-        type: "string",
-      },
-    },
-  },
-  required: ["firstName", "lastName", "colorType", "age"],
-};
-
-export { catSchema };
diff --git a/src/app/v3/schemas/catSchema.ts b/src/app/v3/schemas/catSchema.ts
new file mode 100644
index 0000000..1956af8
--- /dev/null
+++ b/src/app/v3/schemas/catSchema.ts
@@ -0,0 +1,35 @@
+export const catSchema = {
+  id: '/Cat',
+  type: 'object',
+  properties: {
+    firstName: {
+      type: 'string',
+      description: 'First name of cat',
+    },
+    lastName: {
+      type: 'string',
+      description: 'Last name of cat',
+    },
+    colorType: {
+      type: 'string',
+      description: 'Brief description about the cat color type',
+    },
+    age: {
+      type: 'integer',
+      description: 'A numeric int representing the age of the cat',
+    },
+    nicknames: {
+      type: 'array',
+      items: {
+        type: 'string',
+      },
+    },
+    favoriteMeals: {
+      type: 'array',
+      items: {
+        type: 'string',
+      },
+    },
+  },
+  required: ['firstName', 'lastName', 'colorType', 'age'],
+};
diff --git a/src/app/v3/services/catService.ts b/src/app/v3/services/catService.ts
index ca09e17..998f2e4 100644
--- a/src/app/v3/services/catService.ts
+++ b/src/app/v3/services/catService.ts
@@ -1,7 +1,7 @@
-import * as Cats from "../data/Cat.js";
-import { v4 as uuidv4 } from "uuid";
-import type { Cat, StoredCat } from "../shared/types.js";
-import type { ParsedQs } from "qs";
+import * as Cats from '../data/Cat.js';
+import { v4 as uuidv4 } from 'uuid';
+import type { Cat, StoredCat } from '../shared/types.js';
+import type { ParsedQs } from 'qs';
 
 export const getCats = (params: ParsedQs) => Cats.getAll(params);
 
@@ -11,8 +11,8 @@ export const addCat = (newCat: Cat) => {
   const catToInsert = {
     ...newCat,
     id: uuidv4(),
-    createdAt: new Date().toLocaleString("en-US", { timeZone: "UTC" }),
-    updatedAt: new Date().toLocaleString("en-US", { timeZone: "UTC" }),
+    createdAt: new Date().toLocaleString('en-US', { timeZone: 'UTC' }),
+    updatedAt: new Date().toLocaleString('en-US', { timeZone: 'UTC' }),
   };
   const addedCat = Cats.add(catToInsert);
   return addedCat;
diff --git a/src/app/v3/validators/schemaValidator.ts b/src/app/v3/validators/schemaValidator.ts
index 55e7504..e0c4ec3 100644
--- a/src/app/v3/validators/schemaValidator.ts
+++ b/src/app/v3/validators/schemaValidator.ts
@@ -1,8 +1,8 @@
-import { Validator } from "jsonschema";
-import { catSchema } from "../schemas/catSchema.js";
+import { Validator } from 'jsonschema';
+import { catSchema } from '../schemas/catSchema.js';
 
 export const validateInput = (body: object) => {
   const v = new Validator();
-  v.addSchema(catSchema, "/Cat");
+  v.addSchema(catSchema, '/Cat');
   return v.validate(body, catSchema);
 };
diff --git a/src/tests/v2/data/utils.test.js b/src/tests/v2/data/utils.test.js
index 3254f3c..d1fbe20 100644
--- a/src/tests/v2/data/utils.test.js
+++ b/src/tests/v2/data/utils.test.js
@@ -1,16 +1,15 @@
+import DBConnection from '../../../app/v2/data/utils.js';
 
-import DBConnection from "../../../app/v2/data/utils.js";
-
-describe("Common util functions tests", () => {
-  describe("Database interaction", () => {
-    test("Should retrieve the data from a json file", () => {
+describe('Common util functions tests', () => {
+  describe('Database interaction', () => {
+    test('Should retrieve the data from a json file', () => {
       const DB = new DBConnection();
       DB.getDatabase();
       expect(DB).toBeDefined();
     });
 
-    test("Should save data into a file", () => {
-      const result = new DBConnection().saveToDatabase("", "data.json");
+    test('Should save data into a file', () => {
+      const result = new DBConnection().saveToDatabase('', 'data.json');
       expect(result).toBeTruthy();
     });
   });
diff --git a/src/tests/v2/services/catService.test.js b/src/tests/v2/services/catService.test.js
index d2f743f..b3624f0 100644
--- a/src/tests/v2/services/catService.test.js
+++ b/src/tests/v2/services/catService.test.js
@@ -1,7 +1,5 @@
-import * as CatService from '../../../app/v2/services/catService.js'
+import * as CatService from '../../../app/v2/services/catService.js';
 
-describe("Cat Service Layer related tests", () => {
-    describe("Get cats", () => {
-        
-    })
-})
\ No newline at end of file
+describe('Cat Service Layer related tests', () => {
+  describe('Get cats', () => {});
+});