diff --git a/app/__init__.py b/app/__init__.py
index e69de29..70ccd92 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -0,0 +1,10 @@
+from sqlalchemy import create_engine
+from sqlalchemy.engine import Engine
+from sqlalchemy.orm import sessionmaker
+
+from app.config import Config
+
+engine: Engine = create_engine(Config.SQLALCHEMY_DATABASE_URI)
+
+Session = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+session = Session()
diff --git a/app/bot.py b/app/bot.py
index 48e0e9a..3f63623 100644
--- a/app/bot.py
+++ b/app/bot.py
@@ -2,34 +2,29 @@ __all__ = ("main",)
 
 from typing import Optional
 
-from aiogram import Bot, Dispatcher, types
+from aiogram import Bot, Dispatcher
 from aiogram.enums import ParseMode
-from aiogram.filters import CommandStart
-from aiogram.types import Message
-from aiogram.utils.markdown import hbold
+
 from app.config import Config
-
-
-dp = Dispatcher()
-
-
-@dp.message(CommandStart())
-async def command_start_handler(message: Message) -> None:
-    await message.answer(f"Hello, {hbold(message.from_user.full_name)}!")
-
-
-@dp.message()
-async def echo_handler(message: types.Message) -> None:
-    try:
-        await message.send_copy(chat_id=message.chat.id)
-    except TypeError:
-        await message.answer("Nice try!")
+from app.handlers import help_command, profile_command, start_command
+from app.middlewares.throttling import ThrottlingMiddleware
 
 
 async def main() -> None:
+    dp = Dispatcher()
+
     bot_token: Optional[str] = Config.BOT_TOKEN
     if bot_token is not None:
         bot = Bot(bot_token, parse_mode=ParseMode.HTML)
+
+        dp.message.middleware(ThrottlingMiddleware(0.5))
+        dp.include_routers(
+            start_command.router,
+            profile_command.router,
+            help_command.router,
+        )
+
+        await bot.delete_webhook(drop_pending_updates=True)
         await dp.start_polling(bot)
     else:
         exit("BOT_TOKEN is not set")
diff --git a/app/config.py b/app/config.py
index 36691bb..034d344 100644
--- a/app/config.py
+++ b/app/config.py
@@ -8,5 +8,8 @@ load_dotenv()
 
 
 class Config:
-    BOT_TOKEN = os.getenv("BOT_TOKEN")
-    SQLALCHEMY_DATABASE_URI = os.getenv("SQLALCHEMY_DATABASE_URI")
+    BOT_TOKEN = os.getenv("BOT_TOKEN", "")
+    SQLALCHEMY_DATABASE_URI = os.getenv(
+        "SQLALCHEMY_DATABASE_URI",
+        "sqlite:///database.db",
+    )
diff --git a/app/filters/user_filter.py b/app/filters/user_filter.py
new file mode 100644
index 0000000..af01c86
--- /dev/null
+++ b/app/filters/user_filter.py
@@ -0,0 +1,27 @@
+__all__ = ("Unregistered", "Registered", "RegisteredCallback")
+
+from aiogram.filters import Filter
+from aiogram.types import CallbackQuery, Message
+
+from app.models.user import User
+
+
+class Unregistered(Filter):
+    async def __call__(self, message: Message) -> bool:
+        if message.from_user is None:
+            return False
+
+        return not User.user_by_telegram_id_exist(message.from_user.id)
+
+
+class Registered(Filter):
+    async def __call__(self, message: Message) -> bool:
+        if message.from_user is None:
+            return False
+
+        return User.user_by_telegram_id_exist(message.from_user.id)
+
+
+class RegisteredCallback(Filter):
+    async def __call__(self, callback: CallbackQuery) -> bool:
+        return User.user_by_telegram_id_exist(callback.from_user.id)
diff --git a/app/handlers/help_command.py b/app/handlers/help_command.py
new file mode 100644
index 0000000..ab6dff9
--- /dev/null
+++ b/app/handlers/help_command.py
@@ -0,0 +1,16 @@
+__all__ = ()
+
+from aiogram import Router
+from aiogram.filters import Command
+from aiogram.types import Message
+
+from app import messages
+from app.filters.user_filter import Registered
+
+
+router = Router(name="help_command")
+
+
+@router.message(Command("help"), Registered())
+async def command_help_handler(message: Message) -> None:
+    await message.answer(messages.HELP_MESSAGE)
diff --git a/app/handlers/profile_command.py b/app/handlers/profile_command.py
new file mode 100644
index 0000000..80fec4e
--- /dev/null
+++ b/app/handlers/profile_command.py
@@ -0,0 +1,31 @@
+# type: ignore
+__all__ = ()
+
+from aiogram import Router
+from aiogram.filters import Command
+from aiogram.types import Message
+
+from app import messages
+from app.filters.user_filter import Registered
+from app.keyboards.profile import get
+from app.models.user import User
+
+
+router = Router(name="profile_command")
+
+
+@router.message(Command("profile"), Registered())
+async def command_profile_handler(message: Message) -> None:
+    user = User().get_user_by_telegram_id(message.from_user.id)
+
+    await message.answer(
+        messages.PROFILE.format(
+            username=user.username,
+            age=user.age,
+            bio=user.bio if user.bio else messages.NOT_SET,
+            sex=user.sex.capitalize(),
+            country=user.country,
+            city=user.city,
+        ),
+        reply_markup=get(),
+    )
diff --git a/app/handlers/start_command.py b/app/handlers/start_command.py
new file mode 100644
index 0000000..be04bc2
--- /dev/null
+++ b/app/handlers/start_command.py
@@ -0,0 +1,179 @@
+# type: ignore
+__all__ = ()
+
+from aiogram import F, Router
+from aiogram.filters import CommandStart
+from aiogram.fsm.context import FSMContext
+from aiogram.types import Message, ReplyKeyboardRemove
+
+from app import messages, session
+from app.keyboards.builders import profile
+from app.models.user import User
+from app.utils.states import RegistrationForm
+
+
+router = Router(name="start_command")
+
+
+@router.message(CommandStart())
+async def command_start_handler(message: Message, state: FSMContext) -> None:
+    if (
+        User.get_user_by_telegram_id(
+            telegram_id=message.from_user.id,
+        )
+        is not None
+    ):
+        await message.answer(
+            messages.WELCOME_AGAIN_MESSAGE.format(
+                name=message.from_user.full_name,
+            ),
+        )
+    else:
+        await message.answer(
+            messages.WELCOME_MESSAGE.format(
+                name=message.from_user.full_name,
+            ),
+        )
+
+        await state.set_state(RegistrationForm.username)
+        await message.answer(messages.INPUT_USERNAME)
+
+
+@router.message(RegistrationForm.username, F.text)
+async def username_handler(message: Message, state: FSMContext) -> None:
+    username = message.text.strip()
+
+    try:
+        validated_username = User().validate_username(
+            key="username",
+            value=username,
+        )
+    except AssertionError as e:
+        await message.answer(str(e))
+        return
+
+    await state.update_data(username=validated_username)
+    await state.set_state(RegistrationForm.age)
+
+    await message.answer(
+        messages.INPUT_CALLBACK.format(
+            key="username",
+            value=validated_username,
+        ),
+    )
+    await message.answer(messages.INPUT_AGE)
+
+
+@router.message(RegistrationForm.age, F.text)
+async def age_handler(message: Message, state: FSMContext) -> None:
+    age = message.text.strip()
+
+    try:
+        validated_age = User().validate_age(key="age", value=age)
+    except AssertionError as e:
+        await message.answer(str(e))
+        return
+
+    await state.update_data(age=validated_age)
+    await state.set_state(RegistrationForm.sex)
+
+    await message.answer(
+        messages.INPUT_CALLBACK.format(key="age", value=validated_age),
+    )
+    await message.answer(
+        messages.INPUT_SEX,
+        reply_markup=profile(["Male", "Female"]),
+    )
+
+
+@router.message(RegistrationForm.sex, F.text)
+async def sex_handler(message: Message, state: FSMContext) -> None:
+    sex = message.text.strip().lower()
+
+    if sex not in ["male", "female"]:
+        await message.answer(messages.VALIDATION_ERROR_MESSAGE)
+        return
+
+    await state.update_data(sex=sex)
+    await state.set_state(RegistrationForm.bio)
+
+    await message.answer(
+        messages.INPUT_CALLBACK.format(key="sex", value=sex),
+        reply_markup=ReplyKeyboardRemove(),
+    )
+    await message.answer(messages.INPUT_BIO)
+
+
+@router.message(RegistrationForm.bio, F.text)
+async def bio_handler(message: Message, state: FSMContext) -> None:
+    bio = message.text.strip()
+
+    if bio == "/skip":
+        await state.update_data(bio=None)
+        await state.set_state(RegistrationForm.location)
+
+        await message.answer(messages.INPUT_BIO_SKIPPED)
+        await message.answer(messages.INPUT_LOCATION)
+    else:
+        try:
+            validated_bio = User().validate_bio(key="bio", value=bio)
+        except AssertionError as e:
+            await message.answer(str(e))
+            return
+
+        await state.update_data(bio=validated_bio)
+        await state.set_state(RegistrationForm.location)
+
+        await message.answer(
+            messages.INPUT_CALLBACK.format(key="bio", value=validated_bio),
+        )
+        await message.answer(messages.INPUT_LOCATION)
+
+
+@router.message(RegistrationForm.location, F.text)
+async def location_handler(message: Message, state: FSMContext) -> None:
+    location = message.text.strip().split(", ")
+
+    if len(location) != 2:
+        await message.answer(messages.VALIDATION_ERROR_MESSAGE)
+        return
+
+    country, city = location
+
+    try:
+        validated_country = User().validate_country(
+            key="country",
+            value=country,
+        )
+    except AssertionError as e:
+        await message.answer(str(e))
+        return
+
+    try:
+        validated_city = User().validate_city(
+            city=city,
+            country=validated_country,
+        )
+    except AssertionError as e:
+        await message.answer(str(e))
+        return
+
+    await state.update_data(location=[validated_country, validated_city])
+    data = await state.get_data()
+    await state.clear()
+
+    await message.answer(
+        messages.INPUT_CALLBACK.format(
+            key="location",
+            value=", ".join([validated_country, validated_city]),
+        ),
+    )
+
+    data["telegram_id"] = message.from_user.id
+    data["country"] = data["location"][0]
+    data["city"] = data["location"][1]
+    del data["location"]
+    session.add(User(**data))
+    session.commit()
+
+    await message.answer(messages.REGISTERED_MESSAGE)
diff --git a/app/keyboards/builders.py b/app/keyboards/builders.py
new file mode 100644
index 0000000..b7538e5
--- /dev/null
+++ b/app/keyboards/builders.py
@@ -0,0 +1,13 @@
+__all__ = ("profile",)
+
+from aiogram.utils.keyboard import ReplyKeyboardBuilder
+
+
+def profile(text: str | list):
+    builder = ReplyKeyboardBuilder()
+
+    if isinstance(text, str):
+        text = [text]
+
+    [builder.button(text=txt) for txt in text]
+    return builder.as_markup(resize_keyboard=True)
diff --git a/app/keyboards/profile.py b/app/keyboards/profile.py
new file mode 100644
index 0000000..3728912
--- /dev/null
+++ b/app/keyboards/profile.py
@@ -0,0 +1,37 @@
+__all__ = ("get",)
+
+from aiogram import types
+from aiogram.utils.keyboard import InlineKeyboardBuilder
+
+
+def get():
+    builder = InlineKeyboardBuilder()
+
+    builder.row(
+        types.InlineKeyboardButton(
+            text="👤 Change username",
+            callback_data="profile_change_username",
+        ),
+        types.InlineKeyboardButton(
+            text="🔢 Change age",
+            callback_data="profile_change_age",
+        ),
+    )
+    builder.row(
+        types.InlineKeyboardButton(
+            text="ℹ️ Change bio",
+            callback_data="profile_change_bio",
+        ),
+        types.InlineKeyboardButton(
+            text="📝 Change sex",
+            callback_data="profile_change_sex",
+        ),
+    )
+    builder.row(
+        types.InlineKeyboardButton(
+            text="🗺️ Change location",
+            callback_data="profile_change_location",
+        ),
+    )
+
+    return builder.as_markup()
diff --git a/app/messages.py b/app/messages.py
new file mode 100644
index 0000000..77e0a3c
--- /dev/null
+++ b/app/messages.py
@@ -0,0 +1,28 @@
+# flake8: noqa
+
+WELCOME_MESSAGE = "Hello, <b>{name}</b>! Welcome to the ✈️ Travel Agent bot! Let's start our journey by filling out some information about you."
+WELCOME_AGAIN_MESSAGE = "Hello, <b>{name}</b>! Welcome back to the ✈️ Travel Agent bot! If you get lost, you can always call the /help command for assistance."
+
+HELP_MESSAGE = "Help message text."
+
+REGISTERED_MESSAGE = "You have successfully registered. Welcome to the ✈️ Travel Agent bot! \nYou can view and edit your profile using the /profile command."
+
+INPUT_USERNAME = "Enter your username (this will be used to interact with other users):\n<i>Allowed characters: a-z, A-Z, 0-9, _</i>\n<i>Length: 5-20 characters</i>"
+INPUT_AGE = "Enter your age:\n<i>Range: 13-120</i>"
+INPUT_SEX = "Enter your sex:\n<i>Options: Male or Female</i>"
+INPUT_BIO = "Enter your bio (enter /skip if you want to skip this step):\n<i>Maximum length: 100 characters</i>"
+INPUT_BIO_SKIPPED = "Sure. You can always fill it later."
+INPUT_LOCATION = "Enter your location in this format:\n<i>Format: country, city</i>\n<i>Example: Russia, Moscow</i>"
+INPUT_CALLBACK = "All right, your <b>{key}</b> is set to: <b>{value}</b>"
+VALIDATION_ERROR_MESSAGE = "Invalid input. Please try again."
+
+PROFILE = (
+    "<b>Your profile:</b>\n\n"
+    "\tUsername: <b>{username}</b>\n"
+    "\tAge: <b>{age}</b>\n"
+    "\tSex: <b>{sex}</b>\n"
+    "\tBio: <b>{bio}</b>\n"
+    "\tCountry: <b>{country}</b>\n"
+    "\tCity: <b>{city}</b>"
+)
+NOT_SET = "<i>Not set</i>"
diff --git a/app/middlewares/throttling.py b/app/middlewares/throttling.py
new file mode 100644
index 0000000..5da372e
--- /dev/null
+++ b/app/middlewares/throttling.py
@@ -0,0 +1,26 @@
+__all__ = ("ThrottlingMiddleware",)
+
+from typing import Any, Awaitable, Callable, Dict
+
+from aiogram import BaseMiddleware
+from aiogram.types import Message
+from cachetools import TTLCache  # type: ignore
+
+
+class ThrottlingMiddleware(BaseMiddleware):
+
+    def __init__(self, time_limit: int | float = 2) -> None:
+        self.limit = TTLCache(maxsize=10_000, ttl=time_limit)
+
+    async def __call__(
+        self,
+        handler: Callable[[Message, Dict[str, Any]], Awaitable[Any]],
+        event: Message,  # type: ignore
+        data: Dict[str, Any],
+    ) -> Any | None:
+        if event.chat.id in self.limit:
+            return None
+
+        self.limit[event.chat.id] = None
+
+        return await handler(event, data)
diff --git a/app/migrations/README b/app/migrations/README
deleted file mode 100644
index 98e4f9c..0000000
--- a/app/migrations/README
+++ /dev/null
@@ -1 +0,0 @@
-Generic single-database configuration.
\ No newline at end of file
diff --git a/app/migrations/env.py b/app/migrations/env.py
index 4177dec..b05ea8a 100644
--- a/app/migrations/env.py
+++ b/app/migrations/env.py
@@ -4,11 +4,12 @@ from logging.config import fileConfig
 import os
 
 from alembic import context
-from app.models import Base
 from dotenv import load_dotenv
 from sqlalchemy import engine_from_config
 from sqlalchemy import pool
 
+from app.models.user import Base
+
 
 load_dotenv()
 
diff --git a/app/migrations/versions/5896f08fbd61_added_user_model.py b/app/migrations/versions/5896f08fbd61_added_user_model.py
new file mode 100644
index 0000000..c6769c4
--- /dev/null
+++ b/app/migrations/versions/5896f08fbd61_added_user_model.py
@@ -0,0 +1,42 @@
+"""Added User model
+
+Revision ID: 5896f08fbd61
+Revises: 
+Create Date: 2024-03-19 23:25:50.458639
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '5896f08fbd61'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table(
+        'users',
+        sa.Column('telegram_id', sa.Integer(), nullable=False),
+        sa.Column('username', sa.String(length=20), nullable=False),
+        sa.Column('age', sa.SmallInteger(), nullable=False),
+        sa.Column('bio', sa.String(length=100), nullable=True),
+        sa.Column('sex', sa.String(length=6), nullable=True),
+        sa.Column('country', sa.Text(), nullable=False),
+        sa.Column('city', sa.Text(), nullable=False),
+        sa.PrimaryKeyConstraint('telegram_id'),
+        sa.UniqueConstraint('username'),
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_table('users')
+    # ### end Alembic commands ###
diff --git a/app/models.py b/app/models.py
deleted file mode 100644
index 357cd94..0000000
--- a/app/models.py
+++ /dev/null
@@ -1,19 +0,0 @@
-__all__ = ("User",)
-
-from typing import Any
-
-from sqlalchemy import Column, Integer, SmallInteger, String
-from sqlalchemy.ext.declarative import declarative_base
-
-
-Base: Any = declarative_base()
-
-
-class User(Base):
-    __tablename__ = "users"
-
-    telegram_id: Column[int] = Column(Integer, primary_key=True)
-    age: Column[int] = Column(SmallInteger, nullable=False)
-    bio: Column[str] = Column(String(100), nullable=True)
-    country: Column[str] = Column(String(100), nullable=False)
-    city: Column[str] = Column(String(100), nullable=False)
diff --git a/app/models/user.py b/app/models/user.py
new file mode 100644
index 0000000..af1e7d9
--- /dev/null
+++ b/app/models/user.py
@@ -0,0 +1,89 @@
+__all__ = ("User",)
+
+import re
+from typing import Any
+
+import sqlalchemy as sa
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import validates
+
+from app import session
+from app.utils import geo
+
+
+Base: Any = declarative_base()
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    telegram_id = sa.Column(sa.Integer, primary_key=True)
+    username = sa.Column(sa.String(20), nullable=False, unique=True)
+    age = sa.Column(sa.SmallInteger, nullable=False)
+    bio = sa.Column(sa.String(100), nullable=True)
+    sex = sa.Column(sa.String(6), nullable=True)
+    country = sa.Column(sa.Text, nullable=False)
+    city = sa.Column(sa.Text, nullable=False)
+
+    @validates("username")
+    def validate_username(self, key, value):
+        regex_pattern = re.compile(r"^[a-zA-Z0-9_]{5,20}$")
+
+        assert len(value) <= 20, "Username must be 20 characters or fewer."
+        assert len(value) >= 5, "Username must be at least 5 characters."
+        assert (
+            re.match(regex_pattern, value) is not None
+        ), "a-z, A-Z, 0-9, _ only allowed in username."
+
+        return value
+
+    @validates("age")
+    def validate_age(self, key, value):
+        assert str(value).isnumeric(), "Invalid input. Please try again."
+        value = int(value)
+        assert value >= 13, "You must be at least 13 years old."
+        assert value <= 120, "You must be less than 120 years old."
+
+        return value
+
+    @validates("bio")
+    def validate_bio(self, key, value):
+        if value is not None:
+            assert len(value) <= 100, "Bio must be 100 characters or fewer."
+
+        return value
+
+    @validates("country")
+    def validate_country(self, key, value):
+        verdict, normalized_value = geo.validate_country(
+            value,
+        )
+
+        assert verdict, "There is no such country."
+
+        return normalized_value
+
+    def validate_city(self, city, country):
+        verdict, normalized_value = geo.validate_city(
+            city,
+            country,
+        )
+
+        assert verdict, "There is no such city in selected country."
+
+        return normalized_value
+
+    @classmethod
+    def get_user_by_telegram_id(cls, telegram_id):
+        return (
+            session.query(cls).filter(cls.telegram_id == telegram_id).first()
+        )
+
+    @classmethod
+    def user_by_telegram_id_exist(cls, telegram_id):
+        return (
+            cls.get_user_by_telegram_id(
+                telegram_id=telegram_id,
+            )
+            is not None
+        )
diff --git a/app/utils/__init__.py b/app/utils/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/utils/geo.py b/app/utils/geo.py
new file mode 100644
index 0000000..8574f6f
--- /dev/null
+++ b/app/utils/geo.py
@@ -0,0 +1,66 @@
+# type: ignore
+__all__ = ("validate_country", "validate_city")
+
+from geopy.exc import GeocoderTimedOut
+from geopy.geocoders import Nominatim
+
+
+def validate_country(country: str):
+    geolocator = Nominatim(user_agent="travel_agent_bot")
+
+    for _ in range(3):
+        try:
+            geocode = geolocator.geocode(
+                country,
+                featuretype="country",
+            )
+            break
+        except GeocoderTimedOut:
+            continue
+    else:
+        return False, None
+
+    if not geocode:
+        return False, None
+
+    is_loc_country = geocode.raw.get(
+        "type", None,
+    ) == "administrative"
+
+    if is_loc_country:
+        normalized_country = geocode.raw.get("name", "Invalid country")
+        return True, normalized_country
+
+    return False, None
+
+
+def validate_city(city: str, country: str):
+    geolocator = Nominatim(user_agent="travel_agent_bot")
+
+    location_name = f"{country}, {city}"
+    valid_list = ["city", "town", "administrative"]
+
+    for _ in range(3):
+        try:
+            geocode = geolocator.geocode(
+                location_name,
+                featuretype="city",
+            )
+            break
+        except GeocoderTimedOut:
+            continue
+    else:
+        return False, None
+
+    if not geocode:
+        return False, None
+
+    check_in_valid = geocode.raw.get(
+        "type", None,
+    ) in valid_list
+
+    if geocode and check_in_valid:
+        normalized_country = geocode.raw.get("name", "Invalid city")
+        return True, normalized_country
+
+    return False, None
diff --git a/app/utils/states.py b/app/utils/states.py
new file mode 100644
index 0000000..6eb8429
--- /dev/null
+++ b/app/utils/states.py
@@ -0,0 +1,15 @@
+__all__ = ("RegistrationForm",)
+
+from aiogram.fsm.state import State, StatesGroup
+
+
+class RegistrationForm(StatesGroup):
+    username = State()
+    age = State()
+    bio = State()
+    sex = State()
+    location = State()
+
+
+class UserAltering(StatesGroup):
+    new_value = State()
diff --git a/requirements/lints.txt b/requirements/lints.txt
index 16319a5..7a2dc33 100644
--- a/requirements/lints.txt
+++ b/requirements/lints.txt
@@ -13,7 +13,6 @@ flake8-import-order
 flake8-print
 flake8-quotes
 flake8-return
-flake8-type-ignore
 flake8-use-pathlib
 flake8_implicit_str_concat
 pep8-naming
diff --git a/requirements/prod.txt b/requirements/prod.txt
index f7959a9..575c28b 100644
--- a/requirements/prod.txt
+++ b/requirements/prod.txt
@@ -1,5 +1,7 @@
 aiogram==3.4.1
 alembic==1.13.1
+cachetools==5.3.3
+geopy==2.4.1
 psycopg2-binary==2.9.9
 python-dotenv==1.0.1
 sqlalchemy==2.0.28