diff --git a/mlp_api/mlp_api/__init__.py b/mlp_api/mlp_api/__init__.py
index e69de29..fb989c4 100644
--- a/mlp_api/mlp_api/__init__.py
+++ b/mlp_api/mlp_api/__init__.py
@@ -0,0 +1,3 @@
+from .celery import app as celery_app
+
+__all__ = ('celery_app',)
diff --git a/mlp_api/mlp_api/celery.py b/mlp_api/mlp_api/celery.py
new file mode 100644
index 0000000..86d75ab
--- /dev/null
+++ b/mlp_api/mlp_api/celery.py
@@ -0,0 +1,18 @@
+import os
+from celery import Celery
+
+# set default environment variable to the 'celery' program:
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'mlp_api.settings')
+
+# create celery app and set related module's name ('mlp_api')
+app = Celery('mlp_api')
+
+# Configure celery app using django's settings
+# 'namespace' argument needs for refference to celery's settings in settings.py
+# for example: 'CELERY_BROKER_URL' for message broker
+app.config_from_object('django.conf:settings', namespace='CELERY')
+
+# If we need specify task for some django app, we can create 'tasks.py' in app's
+# directory, create there required task, and say to celery app find all
+# these django-app-specified tasks automatically
+app.autodiscover_tasks()
diff --git a/mlp_api/mlp_api/settings.py b/mlp_api/mlp_api/settings.py
index bff4a79..58e3ed9 100644
--- a/mlp_api/mlp_api/settings.py
+++ b/mlp_api/mlp_api/settings.py
@@ -190,6 +190,11 @@
     ),
 }
 
+# Celery configuration:
+CELERY_TASK_SERIALIZER = 'pickle'
+CELERY_RESULT_SERIALIZER = 'pickle'
+CELERY_ACCEPT_CONTENT = ['json', 'pickle']
+
 
 # Include settings for develop
 # File named settings_dev.py
diff --git a/mlp_api/projectApp/models.py b/mlp_api/projectApp/models.py
index ef7c0c6..4046657 100644
--- a/mlp_api/projectApp/models.py
+++ b/mlp_api/projectApp/models.py
@@ -1,3 +1,4 @@
+from io import BytesIO
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
 from django.core.validators import (
@@ -6,10 +7,10 @@
     FileExtensionValidator
 )
 from django.utils.text import slugify
-
 from tinymce.models import HTMLField
-from projectApp.validators import FileSizeValidator
-
+from projectApp.tasks import process_project_preview
+from projectApp.utils import get_project_preview_path
+from utils.validators import FileSizeValidator
 
 class Project(models.Model):
     """Represents project, published on the web-site."""
@@ -30,7 +31,7 @@ class Project(models.Model):
     )
     preview = models.ImageField(
         _('preview'),
-        upload_to='projectApp/previews/',
+        upload_to=get_project_preview_path,
         validators=[
             FileExtensionValidator(allowed_extensions=['jpg', 'jpeg']),
             FileSizeValidator(2.5 * 1024 * 1024)
@@ -75,21 +76,44 @@ class Meta:
         verbose_name = _("enrolled project")
         verbose_name_plural = _("enrolled projects")
 
+    def _prepare_preview_update(self):
+        """
+        Checks if there is some difference between present and old images, like:
+        old was replaced or removed, or old doesn't exist and a new was passed.
+        Returns dictionary with parameters for image processing task.
+        (dictionary will be empty if nothing of told above will happen).
+        """
+
+        old_qs = Project.objects.filter(pk=self.id)
+        old_preview = old_qs.first().preview if old_qs.exists() else None
+        preview_process_params = {}
+        if self.preview != old_preview:
+            if old_preview:
+                preview_process_params.update({'img_old_path': old_preview.name})
+            if self.preview:
+                img_file = self.preview.file.file
+                # At the moment we don't need to save the whole uploaded image
+                # cause it will do asynchronous celery worker
+                # so let's put an empty byte stream instead actual image file:
+                self.preview.save(self.preview.name, BytesIO(), save=False)
+                preview_process_params.update({
+                    'img_path': self.preview.name,
+                    'img_file': img_file
+                })
+
+        return preview_process_params
+
     def save(self, *args, **kwargs):
         # Update slug field, if it's empty - write slugified title there:
         self.slug = self.slug.lower() if self.slug else slugify(self.title)
-
-        # Check preview, if it has updated, remove old image:
-        try:
-            old_self = Project.objects.get(id=self.id)
-            if (not self.preview) or self.preview != old_self.preview:
-                old_self.preview.delete(save=False)
-        except:
-            # If it's a new project or a first preview, just don't do nothing:
-            pass
+        # Prepare preview update:
+        preview_process_params = self._prepare_preview_update()
 
         super().save(*args, **kwargs)
 
+        if preview_process_params:
+            process_project_preview.delay(**preview_process_params)
+
     def __str__(self):
         return "'%s' project." % self.title
 
diff --git a/mlp_api/projectApp/tasks.py b/mlp_api/projectApp/tasks.py
new file mode 100644
index 0000000..d49b3ed
--- /dev/null
+++ b/mlp_api/projectApp/tasks.py
@@ -0,0 +1,22 @@
+import os
+from celery import shared_task
+from django.conf import settings
+from PIL import Image
+
+@shared_task
+def process_project_preview(img_path=None, img_file=None, img_old_path=None):
+    """
+    The task takes next arguments:
+    img_path, img_old_path - path, relative to MEDIA_ROOT,
+        to corresponding new and old preview images.
+    img_file - a new profile's preview image file, uploaded by user.
+    """
+    if img_old_path is not None:
+        old_preview_abs_path = os.path.join(settings.MEDIA_ROOT, img_old_path)
+        try:
+            os.remove(old_preview_abs_path)
+        except FileNotFoundError:
+            pass
+    if img_path is not None and img_file is not None:
+        preview_abs_path = os.path.join(settings.MEDIA_ROOT, img_path)
+        Image.open(img_file).save(preview_abs_path, 'JPEG')
diff --git a/mlp_api/projectApp/utils.py b/mlp_api/projectApp/utils.py
new file mode 100644
index 0000000..23ecfa9
--- /dev/null
+++ b/mlp_api/projectApp/utils.py
@@ -0,0 +1,8 @@
+from os import path
+
+def get_project_preview_path(instance, filename):
+    """
+    Takes an instance of Project model and name of preview's picture.
+    Returns a path to project's picture relative to MEDIA_ROOT.
+    """
+    return path.join('projectApp', 'previews', instance.slug, filename)
diff --git a/mlp_api/projectApp/validators.py b/mlp_api/projectApp/validators.py
deleted file mode 100644
index a11a72e..0000000
--- a/mlp_api/projectApp/validators.py
+++ /dev/null
@@ -1,59 +0,0 @@
-from django.core.exceptions import ValidationError
-from django.utils.translation import gettext_lazy as _
-from django.utils.deconstruct import deconstructible
-
-@deconstructible
-class FileSizeValidator:
-    """
-    Takes maximum size, allowed for a file, in bytes.
-    Creates validator for a FileField.
-    """
-    message = _(
-        "Ensure that file size are less than %(max_size)s %(prefix)sBytes."
-    )
-    code = 'limit_file_size'
-
-    _decimal_prefixes = ('k', 'M', 'G')
-
-
-    def __init__(self, max_size, message=None, code=None):
-        self.max_size = max_size
-        if message is not None:
-            self.message = message
-        if code is not None:
-            self.code = code
-
-    def __call__(self, value):
-        if value.size > self.max_size:
-            raise ValidationError(
-                self.message,
-                code=self.code,
-                params=self._get_pretty_size_params()
-            )
-
-    def __eq__(self, other):
-        return (
-            isinstance(other, self.__class__) and
-            self.max_size == other.max_size and
-            self.message == other.message and
-            self.code == other.code
-        )
-
-    def _get_pretty_size_params(self):
-        """
-        Returns a dictionary with message parameters
-        (max_size, prefix) as keys, and values, depends on
-        maximum allowed bytes for a file.
-        """
-        max_size = self.max_size
-        prefix = ''
-
-        options_quantity = len(FileSizeValidator._decimal_prefixes)
-        for i in range(options_quantity, 0, -1):
-            base = 1024 ** i
-            if self.max_size >= base:
-                max_size /= base
-                prefix = FileSizeValidator._decimal_prefixes[i - 1]
-                break
-
-        return {'max_size':round(max_size, 2), 'prefix':prefix}
diff --git a/mlp_api/projectApp/views.py b/mlp_api/projectApp/views.py
index d2581d0..709f416 100644
--- a/mlp_api/projectApp/views.py
+++ b/mlp_api/projectApp/views.py
@@ -1,7 +1,7 @@
 from rest_framework import viewsets
 from projectApp.models import Project
 from projectApp.serializers import ProjectSerializer
-from projectApp.permissions import IsAdminUserOrReadOnly
+from utils.permissions import IsAdminUserOrReadOnly
 
 
 class ProjectViewSet(viewsets.ModelViewSet):
diff --git a/mlp_api/requirements.txt b/mlp_api/requirements.txt
index 3bb3dee..9dd6f38 100644
--- a/mlp_api/requirements.txt
+++ b/mlp_api/requirements.txt
@@ -1,7 +1,7 @@
-amqp==1.4.9
+amqp==2.4.2
 anyjson==0.3.3
-billiard==3.3.0.23
-celery==3.1.26.post2
+billiard==3.6.0.0
+celery==4.3.0
 certifi==2019.3.9
 cffi==1.12.3
 chardet==3.0.4
@@ -20,7 +20,7 @@ gunicorn==19.9.0
 idna==2.8
 itypes==1.1.0
 Jinja2==2.10.1
-kombu==3.0.37
+kombu==4.5.0
 MarkupSafe==1.1.1
 openapi-codec==1.3.2
 Pillow==6.0.0
diff --git a/mlp_api/userApp/models.py b/mlp_api/userApp/models.py
index 2c6314d..2f08e3b 100644
--- a/mlp_api/userApp/models.py
+++ b/mlp_api/userApp/models.py
@@ -4,18 +4,17 @@
 from django.db import models
 from django.utils import timezone
 from django.utils.translation import ugettext_lazy as _
-from django.core.mail import send_mail
+from django.utils.crypto import get_random_string
 from django.core.validators import MinLengthValidator, FileExtensionValidator
 from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin
 from django.conf import settings
 from PIL import Image
 from userApp.manager import UserManager
-from userApp.utils import (
-    get_userpic_path,
-    get_thumbnail_name,
-    generate_random_string
-)
-from userApp.validators import MinImageSizeValidator
+from userApp.utils import get_userpic_path
+from userApp.tasks import UserAvatarProcessing
+from utils.tasks import send_email
+from utils.validators import MinImageSizeValidator
+
 
 class User(AbstractBaseUser, PermissionsMixin):
     login = models.CharField(
@@ -57,7 +56,7 @@ def __str__(self):
         return self.login + ": " + self.email
 
     def email_user(self, subject, message, from_email=None, **kwargs):
-        send_mail(subject, message, from_email, [self.email], **kwargs)
+        send_email.delay(subject, message, from_email, [self.email], **kwargs)
 
 
 class UserPersonalData(models.Model):
@@ -100,6 +99,11 @@ class UserPersonalData(models.Model):
         verbose_name=_('user\'s authorizing data')
     )
 
+    process_avatar = UserAvatarProcessing.initialize(
+        avatar_size=(460, 460),
+        avatar_thumbnail_size=(150, 150)
+    )
+
     class Meta:
         verbose_name = _("personal data of a user")
         verbose_name_plural = _("personal data of users")
@@ -108,62 +112,41 @@ def __str__(self):
         names = (self.first_name, self.last_name, self.auth_data.login)
         return "%s %s (%s)" % names
 
-    # Handling user's profile picture:
-    avatar_size = (460, 460) # size in pixels
-    avatar_thumbnail_size = (150, 150) # size in pixels
-
-    def _get_avatar_dir(self):
-        """ Returns path to directory for user's avatar. """
-        user_dir = "user_%s" % self.auth_data.id
-        return os.path.join(settings.MEDIA_ROOT, 'userApp', 'avatar', user_dir)
-
-    def _make_avatar_from_field(self):
-        if not self.avatar: return None
-
-        # Verify if there user picture's directory exists:
-        image_dir = self._get_avatar_dir()
-        if not os.path.exists(image_dir):
-            os.makedirs(image_dir)
-
-        # Resizing given user's picture:
-        correct_image = Image.open(self.avatar.file).resize(self.avatar_size)
-        image_bytestream = io.BytesIO()
-        correct_image.save(image_bytestream, 'JPEG')
-        self.avatar.file = image_bytestream
-
-        # Creating thumbnail:
-        correct_image.thumbnail(self.avatar_thumbnail_size)
-        thumbnail_name = get_thumbnail_name(self.avatar.name)
-        thumbnail_path = os.path.join(image_dir, thumbnail_name)
-        correct_image.save(thumbnail_path, 'JPEG')
-
-    def _update_avatar(self):
-        # Check avatar, if it is updated or removed, delete old image:
+    def _prepare_avatar_update(self):
+        """
+        Checks if there is some difference between present and old images, like:
+        old was replaced or removed, or old doesn't exist and a new was passed.
+        Returns dictionary with parameters for image processing task.
+        (dictionary will be empty if nothing of told above will happen).
+        """
+
         try:
             old_avatar = UserPersonalData.objects.get(id=self.id).avatar
-            # In case of changes of avatar:
-            if self.avatar != old_avatar:
-                # If old avatar is present, it should be removed:
-                if old_avatar:
-                    # Remove avatar thumbnail:
-                    thumbnail_path = os.path.join(
-                        settings.MEDIA_ROOT,
-                        get_thumbnail_name(old_avatar.name)
-                    )
-                    os.remove(thumbnail_path)
-                    # Remove avatar:
-                    old_avatar.delete(save=False)
-
-                # If there is a new avatar, it should be stored:
-                self._make_avatar_from_field()
-
-        except (UserPersonalData.DoesNotExist, FileNotFoundError):
-            self._make_avatar_from_field()
+        except UserPersonalData.DoesNotExist:
+            old_avatar = None
+
+        avatar_processing_params = {}
+        if self.avatar != old_avatar:
+            if old_avatar:
+                avatar_processing_params.update({'img_old_path': old_avatar.name})
+            if self.avatar:
+                img_file = self.avatar.file.file
+                # At the moment we don't need to save the whole uploaded image
+                # cause it will do asynchronous celery worker
+                # so let's put an empty byte stream instead actual image file:
+                self.avatar.save(self.avatar.name, io.BytesIO(), save=False)
+                avatar_processing_params.update({
+                    'img_path': self.avatar.name,
+                    'img_file': img_file
+                })
+
+        return avatar_processing_params
 
     def save(self, *args, **kwargs):
-        self._update_avatar()
+        avatar_update_params = self._prepare_avatar_update()
         super().save(*args, **kwargs)
-
+        if avatar_update_params:
+            self.process_avatar.delay(**avatar_update_params)
 
 class UserProgress(models.Model):
     level = models.PositiveSmallIntegerField(
@@ -257,6 +240,6 @@ def notificate_user(self):
         )
 
     def save(self, *args, **kwargs):
-        self.code = generate_random_string(30, 40)
+        self.code = get_random_string(length=30)
         self.notificate_user()
         super().save(*args, **kwargs)
diff --git a/mlp_api/userApp/tasks.py b/mlp_api/userApp/tasks.py
new file mode 100644
index 0000000..f12385f
--- /dev/null
+++ b/mlp_api/userApp/tasks.py
@@ -0,0 +1,53 @@
+import os
+from celery import current_app
+from django.conf import settings
+from django.utils.text import get_valid_filename
+from PIL import Image
+from userApp.utils import get_thumbnail_name
+from utils.filesystem import remove_directory_files
+
+class UserAvatarProcessing(current_app.Task):
+    """
+    Class-based task for handling user's avatar download event.
+    Initializes with two arguments: avatar size and avatar's thumbnail size,
+    both arguments are tuples with two elements: width, height .
+    """
+    name = 'userApp.tasks.process_user_avatar'
+
+    def __init__(self, avatar_size, avatar_thumbnail_size):
+        self.avatar_size = avatar_size
+        self.avatar_thumbnail_size = avatar_thumbnail_size
+
+    def _make_user_avatar(self, avatar, avatar_file):
+        # Resizing given user's picture:
+        correct_image = Image.open(avatar_file).resize(self.avatar_size)
+        correct_image.save(avatar, 'JPEG')
+        # Creating thumbnail:
+        thumbnail = get_thumbnail_name(avatar)
+        correct_image.thumbnail(self.avatar_thumbnail_size)
+        correct_image.save(thumbnail, 'JPEG')
+
+    def run(self, img_path=None, img_file=None, img_old_path=None):
+        """
+        The task takes next arguments:
+        path, old_path - path, relative to MEDIA_ROOT,
+            to corresponding new and old avatar images.
+        file - a new avatar image file, uploaded by user.
+        """
+
+        if img_old_path is not None:
+            old_avatar = os.path.join(settings.MEDIA_ROOT, img_old_path)
+            avar_dir = os.path.dirname(old_avatar)
+            if os.path.isdir(avar_dir):
+                remove_directory_files(avar_dir)
+        if img_path is not None and img_file is not None:
+            avatar = os.path.join(settings.MEDIA_ROOT, img_path)
+            self._make_user_avatar(avatar, img_file)
+
+    @classmethod
+    def initialize(cls, avatar_size, avatar_thumbnail_size):
+        current_app.tasks.register(cls(
+            avatar_size=avatar_size,
+            avatar_thumbnail_size=avatar_thumbnail_size
+        ))
+        return current_app.tasks[cls.name]
diff --git a/mlp_api/userApp/utils.py b/mlp_api/userApp/utils.py
index 3172eb8..32c5cd4 100644
--- a/mlp_api/userApp/utils.py
+++ b/mlp_api/userApp/utils.py
@@ -1,8 +1,5 @@
 from os import path
 import re
-import random
-from string import ascii_letters, digits
-
 
 def get_userpic_path(instance, filename):
     """
@@ -18,11 +15,3 @@ def get_thumbnail_name(avatar_name):
     Return name of related thumbnail file.
     """
     return re.sub(r'\.jpe?g$', lambda fnd: "_150x150"+fnd.group(0), avatar_name)
-
-def generate_random_string(min_len, max_len, chars=ascii_letters + digits):
-    """
-    Takes minimum and maximum length of output string and one optional argument
-    - sequence of characters, on which a new random string will be based.
-    """
-    randrange = range(random.randrange(min_len, max_len))
-    return ''.join(random.choice(chars) for _ in randrange)
diff --git a/mlp_api/utils/__init__.py b/mlp_api/utils/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/mlp_api/utils/filesystem.py b/mlp_api/utils/filesystem.py
new file mode 100644
index 0000000..f38fddc
--- /dev/null
+++ b/mlp_api/utils/filesystem.py
@@ -0,0 +1,7 @@
+import os
+
+def remove_directory_files(directory):
+    """Removes all files in given directory."""
+    paths = (os.path.join(directory, item) for item in os.listdir(directory))
+    files = (path for path in paths if os.path.isfile(path))
+    for file in files: os.remove(file)
diff --git a/mlp_api/projectApp/permissions.py b/mlp_api/utils/permissions.py
similarity index 100%
rename from mlp_api/projectApp/permissions.py
rename to mlp_api/utils/permissions.py
diff --git a/mlp_api/utils/tasks.py b/mlp_api/utils/tasks.py
new file mode 100644
index 0000000..aa42741
--- /dev/null
+++ b/mlp_api/utils/tasks.py
@@ -0,0 +1,6 @@
+from celery import shared_task
+from django.core.mail import send_mail
+
+@shared_task
+def send_email(subject, message, from_email, to, **kwargs):
+    send_mail(subject, message, from_email, to, **kwargs)
diff --git a/mlp_api/userApp/validators.py b/mlp_api/utils/validators.py
similarity index 61%
rename from mlp_api/userApp/validators.py
rename to mlp_api/utils/validators.py
index 7868f0b..762256a 100644
--- a/mlp_api/userApp/validators.py
+++ b/mlp_api/utils/validators.py
@@ -1,8 +1,70 @@
-from django.utils.deconstruct import deconstructible
-from django.utils.translation import gettext_lazy as _
 from django.core.exceptions import ValidationError
+from django.utils.translation import gettext_lazy as _
+from django.utils.deconstruct import deconstructible
 from PIL import Image
 
+@deconstructible
+class FileSizeValidator:
+    """
+    Takes maximum size, allowed for a file, in bytes.
+    Creates validator for a FileField.
+    """
+    message = _(
+        "Ensure that file size are less than %(max_size)s %(prefix)sBytes."
+    )
+    code = 'limit_file_size'
+
+    _decimal_prefixes = ('k', 'M', 'G')
+
+
+    def __init__(self, max_size, message=None, code=None):
+        self.max_size = max_size
+        if message is not None:
+            self.message = message
+        if code is not None:
+            self.code = code
+
+    def __call__(self, value):
+        try:
+            size = value.size
+        except FileNotFoundError:
+            # In case if image was removed manually from user's directory:
+            raise ValidationError("File was removed from project's directory.")
+
+        if size > self.max_size:
+            raise ValidationError(
+                self.message,
+                code=self.code,
+                params=self._get_pretty_size_params()
+            )
+
+    def __eq__(self, other):
+        return (
+            isinstance(other, self.__class__) and
+            self.max_size == other.max_size and
+            self.message == other.message and
+            self.code == other.code
+        )
+
+    def _get_pretty_size_params(self):
+        """
+        Returns a dictionary with message parameters
+        (max_size, prefix) as keys, and values, depends on
+        maximum allowed bytes for a file.
+        """
+        max_size = self.max_size
+        prefix = ''
+
+        options_quantity = len(FileSizeValidator._decimal_prefixes)
+        for i in range(options_quantity, 0, -1):
+            base = 1024 ** i
+            if self.max_size >= base:
+                max_size /= base
+                prefix = FileSizeValidator._decimal_prefixes[i - 1]
+                break
+
+        return {'max_size':round(max_size, 2), 'prefix':prefix}
+
 @deconstructible
 class ImageSizeValidator:
     """