diff --git a/package.json b/package.json
index c8fdb30..b4660f5 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "module-3": "nodemon --exec babel-node ./src/module-3/index.ts --extensions .ts",
+    "module-4": "nodemon --exec babel-node ./src/module-3/index.ts --extensions .ts",
     "lint": "eslint . --ext .ts"
   },
   "author": "",
diff --git a/src/module-3/controllers/groups.ts b/src/module-3/controllers/groups.ts
new file mode 100644
index 0000000..29ce3e8
--- /dev/null
+++ b/src/module-3/controllers/groups.ts
@@ -0,0 +1,82 @@
+import express from "express";
+import { createValidator } from "express-joi-validation";
+import * as GroupsService from "../services/groups";
+import { Errors, GroupModel } from "../types";
+import { isNull } from "./utils";
+import groupValidationSchema from "./validation/groups";
+
+const validator = createValidator();
+const router = express.Router();
+
+/* Get all groups */
+
+router.get("/", async (req, res) => {
+  try {
+    const groups = await GroupsService.findAll();
+    res.status(200).send(groups);
+  } catch (e) {
+    res.status(500).send(e.message);
+  }
+});
+
+/* Find group by id */
+
+router.get("/:id", async (req, res) => {
+  try {
+    const id = req.params.id;
+    const group = await GroupsService.find(id);
+    if (group) {
+      return res.status(200).send(group);
+    }
+    res.status(404).send("Group not found");
+  } catch (e) {
+    res.status(500).send(e.message);
+  }
+});
+
+/* Create new group */
+
+router.post("/", validator.body(groupValidationSchema), async (req, res) => {
+  try {
+    const body: GroupModel = req.body;
+    const isSuccess = await GroupsService.create(body);
+    if (!isSuccess) {
+      return res.status(400).send("Group with this name is already exists");
+    }
+    res.redirect("/api/groups");
+  } catch (e) {
+    res.status(500).send(e.message);
+  }
+});
+
+/* Delete group */
+
+router.delete("/:id", async (req, res) => {
+  try {
+    const id = req.params.id;
+    const isSuccess = await GroupsService.remove(id);
+    if (isNull(isSuccess)) {
+      return res.status(404).send("Something wrong");
+    }
+    res.redirect("/api/groups");
+  } catch (e) {
+    res.status(500).send(e.message);
+  }
+});
+
+/* Update group */
+
+router.put("/:id", validator.body(groupValidationSchema), async (req, res) => {
+  try {
+    const id = req.params.id;
+    const status = await GroupsService.update(id, req.body);
+    if ((status as Errors).type === "error") {
+      return res.status(404).send((status as Errors).message);
+    }
+    res.redirect("/api/groups");
+  } catch (e) {
+    res.status(500).send(e.message);
+  }
+});
+
+export default router;
diff --git a/src/module-3/controllers/user-groups.ts b/src/module-3/controllers/user-groups.ts
new file mode 100644
index 0000000..e83b280
--- /dev/null
+++ b/src/module-3/controllers/user-groups.ts
@@ -0,0 +1,37 @@
+import express from "express";
+import { createValidator } from "express-joi-validation";
+import { AddUsersToGroupModel } from "../services/types";
+import * as UserGroupsService from "../services/user-groups";
+import userGroupValidationSchema from "./validation/user-groups";
+
+const validator = createValidator();
+const router = express.Router();
+
+/* Get user-groups list */
+
+router.get("/", async (req, res) => {
+  try {
+    const userGroups = await UserGroupsService.findAll();
+    res.status(200).send(userGroups);
+  } catch (e) {
+    res.status(500).send(e.message);
+  }
+});
+
+/* Add user to any group by id*/
+
+router.post(
+  "/",
+  validator.body(userGroupValidationSchema),
+  async (req, res) => {
+    try {
+      const body: AddUsersToGroupModel = req.body;
+      await UserGroupsService.addUsersToGroup(body.groupId, body.userIds);
+      res.redirect("/api/user-groups");
+    } catch (e) {
+      res.status(500).send(e.message);
+    }
+  }
+);
+
+export default router;
diff --git a/src/module-3/controllers/users.ts b/src/module-3/controllers/users.ts
index a64a098..f9b8b9c 100644
--- a/src/module-3/controllers/users.ts
+++ b/src/module-3/controllers/users.ts
@@ -1,7 +1,7 @@
 import express from "express";
 import { createValidator } from "express-joi-validation";
-import { UserModel } from "../types";
 import * as UsersService from "../services/users";
+import { UserModel } from "../types";
 import { isNull } from "./utils";
 import userValidationSchema from "./validation/users";
 
diff --git a/src/module-3/controllers/validation/groups.ts b/src/module-3/controllers/validation/groups.ts
new file mode 100644
index 0000000..dc8136c
--- /dev/null
+++ b/src/module-3/controllers/validation/groups.ts
@@ -0,0 +1,6 @@
+import joi from "joi";
+
+export default joi.object().keys({
+  name: joi.string().alphanum().min(3).max(10).required(),
+  permissions: joi.array().required()
+});
diff --git a/src/module-3/controllers/validation/user-groups.ts b/src/module-3/controllers/validation/user-groups.ts
new file mode 100644
index 0000000..b8cbfc4
--- /dev/null
+++ b/src/module-3/controllers/validation/user-groups.ts
@@ -0,0 +1,6 @@
+import joi from "joi";
+
+export default joi.object().keys({
+  userIds: joi.array().required(),
+  groupId: joi.string().required()
+});
diff --git a/src/module-3/controllers/validation/users.ts b/src/module-3/controllers/validation/users.ts
index 51527c8..0917992 100644
--- a/src/module-3/controllers/validation/users.ts
+++ b/src/module-3/controllers/validation/users.ts
@@ -1,9 +1,7 @@
 import joi from "joi";
 
-const userValidationSchema = joi.object().keys({
+export default joi.object().keys({
   login: joi.string().alphanum().min(3).max(10).required(),
   password: joi.string().alphanum().required(),
   age: joi.number().min(4).max(130).required()
 });
-
-export default userValidationSchema;
diff --git a/src/module-3/data-access/index.ts b/src/module-3/data-access/index.ts
index daaef92..0271528 100644
--- a/src/module-3/data-access/index.ts
+++ b/src/module-3/data-access/index.ts
@@ -9,4 +9,10 @@ if (!process.env.DB_URL) {
 
 const DB_URL = process.env.DB_URL;
 
-export default new Sequelize(DB_URL);
+export default new Sequelize(DB_URL, {
+  pool: {
+    max: 5,
+    min: 0,
+    idle: 10000
+  }
+});
diff --git a/src/module-3/index.ts b/src/module-3/index.ts
index 75b727d..c79e912 100644
--- a/src/module-3/index.ts
+++ b/src/module-3/index.ts
@@ -1,4 +1,6 @@
 import express from "express";
+import groupsRouter from "./controllers/groups";
+import userGroupsRouter from "./controllers/user-groups";
 import usersRouter from "./controllers/users";
 import db from "./data-access";
 
@@ -13,6 +15,10 @@ app.listen(3000, () =>
       )
     )
     .then(() => app.use(express.json()))
-    .then(() => app.use("/api/users", usersRouter))
+    .then(() => {
+      app.use("/api/groups", groupsRouter);
+      app.use("/api/users", usersRouter);
+      app.use("/api/user-groups", userGroupsRouter);
+    })
     .catch((err) => console.error(err))
 );
diff --git a/src/module-3/models/group.ts b/src/module-3/models/group.ts
new file mode 100644
index 0000000..6a66a99
--- /dev/null
+++ b/src/module-3/models/group.ts
@@ -0,0 +1,20 @@
+import { DataTypes, Model, ModelCtor } from "sequelize";
+import db from "../data-access";
+import { GroupModel } from "../types";
+
+const Group: ModelCtor<Model<GroupModel>> = db.define(
+  "groups",
+  {
+    name: {
+      type: DataTypes.STRING
+    },
+    permissions: {
+      type: DataTypes.ARRAY(DataTypes.CHAR)
+    }
+  },
+  {
+    timestamps: false
+  }
+);
+
+export default Group;
diff --git a/src/module-3/models/user-group.ts b/src/module-3/models/user-group.ts
new file mode 100644
index 0000000..aa73e5f
--- /dev/null
+++ b/src/module-3/models/user-group.ts
@@ -0,0 +1,20 @@
+import { DataTypes, Model, ModelCtor } from "sequelize";
+import db from "../data-access";
+import { UserGroupModel } from "../types";
+
+const UserGroup: ModelCtor<Model<UserGroupModel>> = db.define(
+  "user-groups",
+  {
+    groupId: {
+      type: DataTypes.STRING
+    },
+    userId: {
+      type: DataTypes.STRING
+    }
+  },
+  {
+    timestamps: false
+  }
+);
+
+export default UserGroup;
diff --git a/src/module-3/services/groups.ts b/src/module-3/services/groups.ts
new file mode 100644
index 0000000..5dd1bdf
--- /dev/null
+++ b/src/module-3/services/groups.ts
@@ -0,0 +1,85 @@
+import { Model } from "sequelize/types";
+import sequelize from "../data-access";
+import Group from "../models/group";
+import { Errors, GroupModel } from "../types";
+import * as UserGroupsService from "./user-groups";
+import { isEqualsObjects } from "./utils";
+
+export const find = async (id: string) =>
+  Group.findOne({
+    where: {
+      id
+    }
+  });
+
+export const findAll = async () =>
+  Group.findAll({
+    raw: true
+  });
+
+export const create = async (model: GroupModel) => {
+  const { name } = model;
+  const group = await Group.findOne({
+    where: {
+      name
+    }
+  });
+
+  if (group) {
+    return null;
+  }
+
+  return Group.create({
+    ...model
+  });
+};
+
+export const remove = async (id: string) => {
+  const transaction = await sequelize.transaction();
+
+  try {
+    const group = await find(id);
+
+    if (!group) {
+      transaction.rollback();
+      return null;
+    }
+
+    await UserGroupsService.remove(transaction, {
+      groupId: id
+    });
+
+    await group.destroy({ transaction });
+    await transaction.commit();
+  } catch (error) {
+    console.error(error);
+    transaction.rollback();
+  }
+};
+
+export const update = async (
+  id: string,
+  model: GroupModel
+): Promise<Model<GroupModel, GroupModel> | Errors> => {
+  const group = await find(id);
+  const { name, permissions } = model;
+
+  if (!group) {
+    return {
+      type: "error",
+      message: "Group with this id not found"
+    };
+  }
+
+  if (isEqualsObjects(group.get(), model)) {
+    return {
+      type: "error",
+      message: "Input data is equal with exist data. Forbidden"
+    };
+  }
+
+  return group.update({
+    name,
+    permissions
+  });
+};
diff --git a/src/module-3/services/types.ts b/src/module-3/services/types.ts
new file mode 100644
index 0000000..3179ba9
--- /dev/null
+++ b/src/module-3/services/types.ts
@@ -0,0 +1,10 @@
+import { BaseUser, GroupModel, UserGroupModel } from "../types";
+
+export type AddUsersToGroupModel = Omit<UserGroupModel, "userId"> & {
+  userIds: Array<UserGroupModel["userId"]>;
+};
+
+export interface RemoveUserGroupParams {
+  userId?: BaseUser["id"];
+  groupId?: GroupModel["id"];
+}
diff --git a/src/module-3/services/user-groups.ts b/src/module-3/services/user-groups.ts
new file mode 100644
index 0000000..3174849
--- /dev/null
+++ b/src/module-3/services/user-groups.ts
@@ -0,0 +1,86 @@
+import { Transaction } from "sequelize/types";
+import sequelize from "../data-access";
+import UserGroup from "../models/user-group";
+import { UserGroupModel } from "../types";
+import { find as findGroupById } from "./groups";
+import { RemoveUserGroupParams } from "./types";
+import { find as findUserById } from "./users";
+
+export const findAll = async () => UserGroup.findAll();
+
+export const findUserGroup = async (userId: string) =>
+  UserGroup.findOne({
+    where: {
+      userId
+    }
+  });
+
+export const addUsersToGroup = async (
+  groupId: UserGroupModel["groupId"],
+  userIds: Array<UserGroupModel["userId"]>
+) => {
+  const group = findGroupById(groupId);
+  const transaction = await sequelize.transaction();
+
+  try {
+    return sequelize
+      .transaction(async (t) => {
+        for (const userId of userIds) {
+          const user = await findUserById(userId);
+          const isUserGroupExisted = await UserGroup.findOne({
+            where: {
+              groupId,
+              userId
+            }
+          });
+
+          if (!user || !group || isUserGroupExisted) {
+            return;
+          }
+
+          await UserGroup.create(
+            {
+              userId,
+              groupId
+            },
+            { transaction: t }
+          );
+        }
+      })
+      .then(() => {
+        return Promise.resolve();
+      });
+  } catch (error) {
+    console.error(error);
+    await transaction.rollback();
+  }
+};
+
+export const remove = async (
+  transaction: Transaction,
+  params: RemoveUserGroupParams
+) => {
+  const { userId, groupId } = params ?? {};
+  const id = userId ?? groupId;
+
+  if (!id) {
+    return Promise.reject();
+  }
+
+  const userGroups = await UserGroup.findAll({
+    where: {
+      ...(userId ? { userId: id } : undefined),
+      ...(groupId ? { groupId: id } : undefined)
+    }
+  });
+
+  if (!userGroups.length) {
+    return Promise.reject();
+  }
+
+  for (const userGroup of userGroups) {
+    await userGroup.destroy({ transaction });
+  }
+
+  return Promise.resolve();
+};
diff --git a/src/module-3/services/users.ts b/src/module-3/services/users.ts
index 6637d8f..b89ff60 100644
--- a/src/module-3/services/users.ts
+++ b/src/module-3/services/users.ts
@@ -1,5 +1,7 @@
-import { UserModel } from "../types";
+import sequelize from "../data-access";
 import User from "../models/user";
+import { UserModel } from "../types";
+import * as UserGroupsService from "./user-groups";
 
 export const getUsersList = async () =>
   User.findAll({
@@ -50,15 +52,32 @@ export const create = async (model: UserModel) => {
 };
 
 export const remove = async (id: string) => {
-  const user = await find(id);
+  const transaction = await sequelize.transaction();
 
-  if (!user) {
-    return null;
-  }
+  try {
+    const user = await find(id);
+    if (!user) {
+      transaction.rollback();
+      return null;
+    }
 
-  return user.update({
-    isDeleted: true
-  });
+    await UserGroupsService.remove(transaction, {
+      userId: id
+    });
+
+    await user.update(
+      {
+        isDeleted: true
+      },
+      {
+        transaction
+      }
+    );
+    await transaction.commit();
+  } catch (error) {
+    console.error(error);
+    transaction.rollback();
+  }
 };
 
 export const update = async (id: string, model: UserModel) => {
diff --git a/src/module-3/services/utils.ts b/src/module-3/services/utils.ts
new file mode 100644
index 0000000..028c64b
--- /dev/null
+++ b/src/module-3/services/utils.ts
@@ -0,0 +1,11 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
+export const isEqualsObjects = (obj1: any, obj2: any) => {
+  // Delete useless ids here
+  /* eslint-disable @typescript-eslint/no-unused-vars */
+  console.log(obj1, obj2);
+  const { id: id1, ...anotherDataObj1 } = obj1;
+  const { id: id2, ...anotherDataObj2 } = obj2;
+  /* eslint-enable */
+
+  return JSON.stringify(anotherDataObj1) === JSON.stringify(anotherDataObj2);
+};
diff --git a/src/module-3/types.ts b/src/module-3/types.ts
index 8364b99..0a22483 100644
--- a/src/module-3/types.ts
+++ b/src/module-3/types.ts
@@ -1,10 +1,35 @@
+export interface BaseUser {
+  id?: string;
+  isDeleted?: boolean;
+}
+
+export interface BaseGroup {
+  id?: string;
+}
 export interface UserModel extends BaseUser {
   login: string;
   password: string;
   age: number;
 }
 
-export interface BaseUser {
-  id?: string;
-  isDeleted?: boolean;
+export type Permissions =
+  | "READ"
+  | "WRITE"
+  | "DELETE"
+  | "SHARE"
+  | "UPLOAD_FILES";
+
+export interface GroupModel extends BaseGroup {
+  name: string;
+  permissions: Array<Permissions>;
+}
+
+export interface Errors {
+  type: string;
+  message: string;
+}
+
+export interface UserGroupModel {
+  userId: string;
+  groupId: string;
 }