1. Introduction Since I started my journey with programming, I noticed an interesting pattern: the majority of applications are templated. Yes, it’s a pure fact! Just stop right here, at the beginning of this article, and start thinking of all the projects you have developed. What do they have in common? If you look closely, you’ll see that many core functionalities are reused across different projects. These core functionalities often include user authentication, payment processing, user management, and more. In this article, I would like to raise the point that all of these patterns were already created by programmers from the past.Really, almost everything we are using right now, was already implemented. We just modify some functionality based on the specific project. I will introduce you to examples from the backend development perspective in Python, but this can be applied to any programming language or any field in the realm of software engineering. So, what do all backend applications have in common? Let’s take a look! Note: If you are familiar with OOP (Object Oriented Programming), consider your templated modules as the highest level of abstraction but on the application level so that this should be written according to this principle. 2. Authentication and Authorization I would like to break down each further section to the basic components, which can be applied almost to any backend application. Basic Components User Model: A representation of the user that includes attributes like username, password, email, roles, etc. Password Management: Functions to hash and verify passwords. Token Generation: Mechanism to generate and verify tokens (JWT, OAuth2, etc.). Middleware/Decorator: Protect routes/endpoints that require authentication. Role Management: Assign and verify user roles and permissions. 2.1 User Model We are defining the most generic class of the User with attributes that can be applied to any specific user. from werkzeug.security import generate_password_hash, check_password_hash class User: def __init__(self, username, password, email): self.username = username self.password_hash = generate_password_hash(password) self.email = email self.roles = [] def set_password(self, password): self.password_hash = generate_password_hash(password) def check_password(self, password): return check_password_hash(self.password_hash, password) 2.2 Token Management Using JWT for token-based authentication is a good choice in terms of cybersecurity and best practices in backend development. def generate_token(user): payload = { 'username': user.username, 'exp': datetime.datetime.utcnow() + datetime.timedelta(hours=1) } return jwt.encode(payload, SECRET_KEY, algorithm='HS256') def verify_token(token): try: payload = jwt.decode(token, SECRET_KEY, algorithms=['HS256']) return payload['username'] except jwt.ExpiredSignatureError: return None except jwt.InvalidTokenError: return None 2.3 Decorators Decorator to check if the user is allowed to access the page. from functools import wraps from flask import request, jsonify, session def is_authenticated(func): @wraps(func) def decorated_function(*args, **kwargs): if 'user' not in session: return jsonify({"error": "User not authenticated"}), 401 return func(*args, **kwargs) return decorated_function Decorator to check the role of the user. def roles_required(*roles): def decorator(func): @wraps(func) def decorated_function(*args, **kwargs): user_roles = session.get('roles', []) if not any(role in user_roles for role in roles): return jsonify({"error": "User does not have the required role"}), 403 return func(*args, **kwargs) return decorated_function return decorator And basically, that’s it! You can use this predefined functionality for authentication across all projects! 3. Payments and Billing Almost any application handles financial transactions. Whether it’s a local butcher shop or a big enterprise giant, you will need to use an effective system to gather payments. Basic Components Payment Gateway Integration: Connecting with payment gateways like Stripe or PayPal Payment Models: Defining models to handle payment data. Payment Processing: Handling the payment lifecycle (initiate, confirm, etc.). 3.1 Payment Gateway Integration This can be used as a base for integrating different payment gateways, with a concrete implementation for Stripe. Generally, my personal preference is to use StripeAPI for payments as it has been for a long time on the market, and really, easy to integrate into any project. class PaymentGateway(ABC): @abstractmethod def create_payment_intent(self, amount, currency='gbp'): pass @abstractmethod def confirm_payment(self, payment_id): pass @abstractmethod def handle_webhook(self, payload, sig_header): pass This is the most generic example for the payment gateway, and you can focus on specific implementation according to your needs. 3.2 Payment Models Define models to store payment information. This example can be adapted for use with ORM. You may create a more complex hierarchy of classes if needed, but for this example, the following snippet should be pretty sufficient. class Payment: def __init__(self, user_id, amount, currency): self.id = uuid.uuid4() self.user_id = user_id self.amount = amount self.currency = currency self.status = status payments = [] Save all payments into the database and set up a Celery task for processing transactions, for the 3.3 section. The database records should look like the following: id | user_id | amount | currency | status --------------------------------------+-----------------------------------+--------+----------+---------- e532d653-7c8b-453a-8cd4-3ab956863d72 | 1ff9efb3-d5e8-4e53-854f-4246ba9ff638 | 100.00 | USD | Failed 35985d41-5d54-4021-bed6-82d7233cc353 | a0984002-bace-478e-b6f9-6e4459e1b5ba | 250.50 | EUR | Pending 1ff9efb3-d5e8-4e53-854f-4246ba9ff638 | 9f896874-dc43-4592-8289-d0f7f8b8583a | 99.99 | GBP | Completed Now, we have created a complex system that can be integrated into any project. Are you still following the pattern? This can be used EVERYWHERE! After all, you can define another application for visualization of this data. You’ve got the point about templating! 😉 4. Email and Notification Services Email and notifications keep users informed and engaged in the life of your app. Whether it's for account verification, password resets, or marketing communications, a reliable email service is essential for any type of project. Email Service Integration: Connecting with email services like SendGrid or Amazon SES. Email Templates: Defining templates for various email types. Sending Emails: Functions to send emails using the integrated service. 4.1 Email Service Integration Define the main logic of SendGrid for sending emails inside EmailService class. import sendgrid from sendgrid.helpers.mail import Mail class EmailService: def __init__(self, api_key): self.sg = sendgrid.SendGridAPIClient(api_key) def send_email(self, from_email, to_email, subject, html_content): email = Mail( from_email=from_email, to_emails=to_email, subject=subject, html_content=html_content ) try: response = self.sg.send(email) return response.status_code except Exception as e: return str(e) As with payment gateway, you don’t need to focus on any specific utils or products on the market. This is just an example of how it can be generalized and templated for any project. 4.2 Email Templates My favorite pattern for systems like this is the handlers pattern; you just add more and more keys to the dictionary as a type of email, and the path to the file with a content. email_templates = { 'welcome': “welcome.html”, 'reset_password': "<h1>Reset Your Password</h1><p>Click <a href='{link}'>here</a> to reset your password.</p>" } Otherwise, it could be nice to define an Enum for the same purposes. 4.3 Sending Emails We need a function to make the magic happen! Let’s write the following: def send_email(email_service, from_email, to_email, subject, template_name, **template_vars): """ Send an email using the specified email service. """ html_content = get_email_template(template_name, **template_vars) return email_service.send_email(from_email, to_email, subject, html_content) Another important point would be adding several files to all backend projects, such as README .env config.py, pyproject.toml, .pre-commit.yml and come up with the base structure of the files inside the project. Though the suggested structure is a little bit tightened to Python implementation, as I mentioned before, you can do the same for any other language or field. It is also important to note that templating at the highest level of abstraction and maintaining a good structure of the application can be reused for other projects as a package or an addition to the microservice architecture. 5. Conclusion EVERYTHING CAN BE TEMPLATED! The examples provided here are just the beginning—these patterns can be extended and refined to cover more complex scenarios as your projects evolve. You may add caching establish k8s, docker, Devops infrastructure, CI/CD and pipelines. Remember one simple statement: Once you have done your job properly, you can use the same job while completing another. The goal is to make the project, infrastructure, components, and services reusable across different applications! Make yourself a cup of tea, and think about which parts of your applications can be re-used in different apps. Try to create similar services and automate your job, adjusting only some code pieces! Thanks for reading, and happy templating! 1. Introduction Since I started my journey with programming, I noticed an interesting pattern: the majority of applications are templated. Yes, it’s a pure fact! Just stop right here, at the beginning of this article, and start thinking of all the projects you have developed. the majority of applications are templated. What do they have in common? If you look closely, you’ll see that many core functionalities are reused across different projects. These core functionalities often include user authentication, payment processing, user management, and more. What do they have in common? In this article, I would like to raise the point that all of these patterns were already created by programmers from the past. Really, almost everything we are using right now, was already implemented. We just modify some functionality based on the specific project. Really, almost everything we are using right now, was already implemented. I will introduce you to examples from the backend development perspective in Python, but this can be applied to any programming language or any field in the realm of software engineering. So, what do all backend applications have in common? Let’s take a look! So, what do all backend applications have in common? Let’s take a look! So, what do all backend applications have in common? Let’s take a look! Note : If you are familiar with OOP (Object Oriented Programming), consider your templated modules as the highest level of abstraction but on the application level so that this should be written according to this principle. Note application level 2. Authentication and Authorization 2. Authentication and Authorization I would like to break down each further section to the basic components, which can be applied almost to any backend application. Basic Components Basic Components User Model: A representation of the user that includes attributes like username, password, email, roles, etc. Password Management: Functions to hash and verify passwords. Token Generation: Mechanism to generate and verify tokens (JWT, OAuth2, etc.). Middleware/Decorator: Protect routes/endpoints that require authentication. Role Management: Assign and verify user roles and permissions. User Model: A representation of the user that includes attributes like username, password, email, roles, etc. User Model: Password Management: Functions to hash and verify passwords. Password Management: Token Generation: Mechanism to generate and verify tokens (JWT, OAuth2, etc.). Token Generation: Middleware/Decorator: Protect routes/endpoints that require authentication. Middleware/Decorator: Role Management: Assign and verify user roles and permissions. Role Management: 2.1 User Model 2.1 User Model We are defining the most generic class of the User with attributes that can be applied to any specific user. User from werkzeug.security import generate_password_hash, check_password_hash class User: def __init__(self, username, password, email): self.username = username self.password_hash = generate_password_hash(password) self.email = email self.roles = [] def set_password(self, password): self.password_hash = generate_password_hash(password) def check_password(self, password): return check_password_hash(self.password_hash, password) from werkzeug.security import generate_password_hash, check_password_hash class User: def __init__(self, username, password, email): self.username = username self.password_hash = generate_password_hash(password) self.email = email self.roles = [] def set_password(self, password): self.password_hash = generate_password_hash(password) def check_password(self, password): return check_password_hash(self.password_hash, password) 2.2 Token Management 2.2 Token Management Using JWT for token-based authentication is a good choice in terms of cybersecurity and best practices in backend development. def generate_token(user): payload = { 'username': user.username, 'exp': datetime.datetime.utcnow() + datetime.timedelta(hours=1) } return jwt.encode(payload, SECRET_KEY, algorithm='HS256') def verify_token(token): try: payload = jwt.decode(token, SECRET_KEY, algorithms=['HS256']) return payload['username'] except jwt.ExpiredSignatureError: return None except jwt.InvalidTokenError: return None def generate_token(user): payload = { 'username': user.username, 'exp': datetime.datetime.utcnow() + datetime.timedelta(hours=1) } return jwt.encode(payload, SECRET_KEY, algorithm='HS256') def verify_token(token): try: payload = jwt.decode(token, SECRET_KEY, algorithms=['HS256']) return payload['username'] except jwt.ExpiredSignatureError: return None except jwt.InvalidTokenError: return None 2.3 Decorators 2.3 Decorators Decorator to check if the user is allowed to access the page. Decorator to check if the user is allowed to access the page. from functools import wraps from flask import request, jsonify, session def is_authenticated(func): @wraps(func) def decorated_function(*args, **kwargs): if 'user' not in session: return jsonify({"error": "User not authenticated"}), 401 return func(*args, **kwargs) return decorated_function from functools import wraps from flask import request, jsonify, session def is_authenticated(func): @wraps(func) def decorated_function(*args, **kwargs): if 'user' not in session: return jsonify({"error": "User not authenticated"}), 401 return func(*args, **kwargs) return decorated_function Decorator to check the role of the user. Decorator to check the role of the user. def roles_required(*roles): def decorator(func): @wraps(func) def decorated_function(*args, **kwargs): user_roles = session.get('roles', []) if not any(role in user_roles for role in roles): return jsonify({"error": "User does not have the required role"}), 403 return func(*args, **kwargs) return decorated_function return decorator def roles_required(*roles): def decorator(func): @wraps(func) def decorated_function(*args, **kwargs): user_roles = session.get('roles', []) if not any(role in user_roles for role in roles): return jsonify({"error": "User does not have the required role"}), 403 return func(*args, **kwargs) return decorated_function return decorator And basically, that’s it! You can use this predefined functionality for authentication across all projects! 3. Payments and Billing 3. Payments and Billing Almost any application handles financial transactions. Whether it’s a local butcher shop or a big enterprise giant, you will need to use an effective system to gather payments. Basic Components Basic Components Payment Gateway Integration: Connecting with payment gateways like Stripe or PayPal Payment Models: Defining models to handle payment data. Payment Processing: Handling the payment lifecycle (initiate, confirm, etc.). Payment Gateway Integration: Connecting with payment gateways like Stripe or PayPal Payment Gateway Integration: Stripe PayPal Payment Models: Defining models to handle payment data. Payment Models: Payment Processing: Handling the payment lifecycle (initiate, confirm, etc.). Payment Processing: 3.1 Payment Gateway Integration 3.1 Payment Gateway Integration This can be used as a base for integrating different payment gateways, with a concrete implementation for Stripe. Generally, my personal preference is to use StripeAPI for payments as it has been for a long time on the market, and really, easy to integrate into any project. StripeAPI class PaymentGateway(ABC): @abstractmethod def create_payment_intent(self, amount, currency='gbp'): pass @abstractmethod def confirm_payment(self, payment_id): pass @abstractmethod def handle_webhook(self, payload, sig_header): pass class PaymentGateway(ABC): @abstractmethod def create_payment_intent(self, amount, currency='gbp'): pass @abstractmethod def confirm_payment(self, payment_id): pass @abstractmethod def handle_webhook(self, payload, sig_header): pass This is the most generic example for the payment gateway, and you can focus on specific implementation according to your needs. 3.2 Payment Models 3.2 Payment Models Define models to store payment information. This example can be adapted for use with ORM. You may create a more complex hierarchy of classes if needed, but for this example, the following snippet should be pretty sufficient. class Payment: def __init__(self, user_id, amount, currency): self.id = uuid.uuid4() self.user_id = user_id self.amount = amount self.currency = currency self.status = status payments = [] class Payment: def __init__(self, user_id, amount, currency): self.id = uuid.uuid4() self.user_id = user_id self.amount = amount self.currency = currency self.status = status payments = [] Save all payments into the database and set up a Celery task for processing transactions, for the 3.3 section. The database records should look like the following: Celery id | user_id | amount | currency | status --------------------------------------+-----------------------------------+--------+----------+---------- e532d653-7c8b-453a-8cd4-3ab956863d72 | 1ff9efb3-d5e8-4e53-854f-4246ba9ff638 | 100.00 | USD | Failed 35985d41-5d54-4021-bed6-82d7233cc353 | a0984002-bace-478e-b6f9-6e4459e1b5ba | 250.50 | EUR | Pending 1ff9efb3-d5e8-4e53-854f-4246ba9ff638 | 9f896874-dc43-4592-8289-d0f7f8b8583a | 99.99 | GBP | Completed id | user_id | amount | currency | status --------------------------------------+-----------------------------------+--------+----------+---------- e532d653-7c8b-453a-8cd4-3ab956863d72 | 1ff9efb3-d5e8-4e53-854f-4246ba9ff638 | 100.00 | USD | Failed 35985d41-5d54-4021-bed6-82d7233cc353 | a0984002-bace-478e-b6f9-6e4459e1b5ba | 250.50 | EUR | Pending 1ff9efb3-d5e8-4e53-854f-4246ba9ff638 | 9f896874-dc43-4592-8289-d0f7f8b8583a | 99.99 | GBP | Completed Now, we have created a complex system that can be integrated into any project. Are you still following the pattern? This can be used EVERYWHERE! This can be used EVERYWHERE! After all, you can define another application for visualization of this data. You’ve got the point about templating! 😉 4. Email and Notification Services 4. Email and Notification Services Email and notifications keep users informed and engaged in the life of your app. Whether it's for account verification, password resets, or marketing communications, a reliable email service is essential for any type of project. Email Service Integration: Connecting with email services like SendGrid or Amazon SES. Email Templates: Defining templates for various email types. Sending Emails: Functions to send emails using the integrated service. Email Service Integration: Connecting with email services like SendGrid or Amazon SES . Email Service Integration: SendGrid Amazon SES Email Templates: Defining templates for various email types. Email Templates: Sending Emails: Functions to send emails using the integrated service. Sending Emails: 4.1 Email Service Integration 4.1 Email Service Integration Define the main logic of SendGrid for sending emails inside EmailService class. SendGrid EmailService import sendgrid from sendgrid.helpers.mail import Mail class EmailService: def __init__(self, api_key): self.sg = sendgrid.SendGridAPIClient(api_key) def send_email(self, from_email, to_email, subject, html_content): email = Mail( from_email=from_email, to_emails=to_email, subject=subject, html_content=html_content ) try: response = self.sg.send(email) return response.status_code except Exception as e: return str(e) import sendgrid from sendgrid.helpers.mail import Mail class EmailService: def __init__(self, api_key): self.sg = sendgrid.SendGridAPIClient(api_key) def send_email(self, from_email, to_email, subject, html_content): email = Mail( from_email=from_email, to_emails=to_email, subject=subject, html_content=html_content ) try: response = self.sg.send(email) return response.status_code except Exception as e: return str(e) As with payment gateway, you don’t need to focus on any specific utils or products on the market. This is just an example of how it can be generalized and templated for any project. 4.2 Email Templates 4.2 Email Templates My favorite pattern for systems like this is the handlers pattern; you just add more and more keys to the dictionary as a type of email, and the path to the file with a content. email_templates = { 'welcome': “welcome.html”, 'reset_password': "<h1>Reset Your Password</h1><p>Click <a href='{link}'>here</a> to reset your password.</p>" } email_templates = { 'welcome': “welcome.html”, 'reset_password': "<h1>Reset Your Password</h1><p>Click <a href='{link}'>here</a> to reset your password.</p>" } Otherwise, it could be nice to define an Enum for the same purposes. Enum 4.3 Sending Emails 4.3 Sending Emails We need a function to make the magic happen! Let’s write the following: def send_email(email_service, from_email, to_email, subject, template_name, **template_vars): """ Send an email using the specified email service. """ html_content = get_email_template(template_name, **template_vars) return email_service.send_email(from_email, to_email, subject, html_content) def send_email(email_service, from_email, to_email, subject, template_name, **template_vars): """ Send an email using the specified email service. """ html_content = get_email_template(template_name, **template_vars) return email_service.send_email(from_email, to_email, subject, html_content) Another important point would be adding several files to all backend projects, such as README .env config.py , pyproject.toml, .pre-commit.yml and come up with the base structure of the files inside the project. README .env config.py pyproject.toml, .pre-commit.yml come up with the base structure of the files inside the project. Though the suggested structure is a little bit tightened to Python implementation, as I mentioned before, you can do the same for any other language or field. It is also important to note that templating at the highest level of abstraction and maintaining a good structure of the application can be reused for other projects as a package or an addition to the microservice architecture. 5. Conclusion EVERYTHING CAN BE TEMPLATED! EVERYTHING CAN BE TEMPLATED! The examples provided here are just the beginning—these patterns can be extended and refined to cover more complex scenarios as your projects evolve. You may add caching establish k8s , docker , Devops infrastructure, CI/CD and pipelines. caching k8s docker Devops CI/CD Remember one simple statement: Once you have done your job properly, you can use the same job while completing another. Remember one simple statement: The goal is to make the project, infrastructure, components, and services reusable across different applications! The goal is to make the project, infrastructure, components, and services reusable across different applications! Make yourself a cup of tea, and think about which parts of your applications can be re-used in different apps. Try to create similar services and automate your job, adjusting only some code pieces! Thanks for reading, and happy templating!
