Monolith vs Microservices

The architecture that shapes your app's future

When you're building an app, the architecture you choose can make or break its success. While most users never see the inner workings of an app, the design behind the scenes plays a crucial role in how your app scales, performs, and adapts to growing demands.We'll delve into two widespread architectural approaches: monolith and microservices, and see how they influence everything from development to scalability. Understanding different architectures is essential for making intelligent choices, whether you're developing a new app or redesigning an existing one.

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Think of it like building a house

In monolithic architecture, everything is built as part of one unified system. Think of it like constructing a giant skyscraper where everything is housed in one place. This is a single, large codebase where all the features of your app are integrated and run together. You don’t have separate "buildings" or services; everything is bundled into a single unit.

This architecture diagram illustrates monolithic architecture in retail, where all core services—such as inventory management, order processing, customer service, payments, and shipping—are tightly integrated into a unified system, making deployment and scaling centralized but less flexible.

Monolithic architecture code


class OrderService:
    def __init__(self, db):
        self.db = db

    def place_order(self, user_id, product_id):
        user = self.db.get_user(user_id)
        product = self.db.get_product(product_id)
        if user and product:
            self.db.create_order(user_id, product_id)
            return "Order placed successfully!"
        return "Order failed."

# Everything interacts within the same system
class Database:
    def get_user(self, user_id):
      # Query database for user
      pass

    def get_product(self, product_id):
      # Query database for product
      pass

    def create_order(self, user_id, product_id):
      # Insert order into database
      pass

In a monolithic approach, all services (such as user authentication, orders, and payments) exist within a single codebase and share a common database.

The code represents a monolithic approach where all operations (user retrieval, product lookup, and order creation) are handled within a single, tightly coupled system.

While simple to implement, this approach can become difficult to scale as the application grows.

Advantages of monolithic architecture

Simplicity

It’s easier to get started with a monolith. For startups building their first app, a monolithic approach can get you to your minimum viable product (MVP) quickly.

Fewer moving parts

With everything in one place, it's easier to manage and deploy updates, at least in the early stages.

Faster time to market

If you're testing ideas quickly, a monolith is often the quickest route to getting something out there.

Challenges of Monoliths

Tight Coupling

However, as your app grows, so does its complexity. Making changes to monolithic architecture can become cumbersome because one change in a single module could impact the entire system.

Scaling

When it comes to scaling, monolithic architecture is about vertical scaling. Imagine making your skyscraper taller by adding more resources—more memory and more powerful servers—but you’re still confined to that single structure. Scaling is limited by the boundaries of the system you’ve built.

Breaking it down into manageable parts

On the flip side, microservices are like building a city with several interconnected but independent buildings. Instead of one giant codebase, microservices break down your app into smaller, specialized services. Each service is independently developed, deployed, and scaled. This distributed approach allows each part of your app to evolve and grow at its own pace.

This architecture diagram illustrates microservices architecture in retail, where services—such as vendor management, order processing, customer service, payments, and shipping—are developed as independent, loosely coupled services, enabling flexible deployment and independent scaling.

Microservices architecture code

In a microservices approach, different services (such as user, order, and payment services) communicate with each other via APIs.

User service


from flask import Flask, request, jsonify

app = Flask(__name__)

users = {"1": {"name": "John Doe", "email": "john@example.com"}}

@app.route("/user/", methods=["GET"])
def get_user(user_id):
    user = users.get(user_id)
    if user:
        return jsonify(user), 200 # Return user with HTTP 200
    return jsonify({"error": "User not found"}), 404 # Return 404 if user is missing

if __name__ == "__main__":
    app.run(port=5001)

Here, the user service, product service, and order service are independent. The order service fetches the needed data via an API call instead of relying on a shared database, reducing dependencies and improving scalability.

Product service


from flask import Flask, jsonify

app = Flask(__name__)

# Mock product database
products = []
@app.route('/products/', methods=['GET'])
def get_product(product_id):
    product = products.get(product_id)
    if not product:
        return jsonify({"error": "Product not found"}), 404
    return jsonify({"product_id": product_id, **product})

if __name__ == '__main__':
    app.run(port=5001, debug=True)

Order service


from flask import Flask, request, jsonify

app = Flask(__name__)

# Mock orders DB
orders = []

@app.route('/orders', methods=['POST'])
def place_order():
    data = request.json
    if not data or "product_id" not in data or "quantity" not in data:
        return jsonify({"error": "Invalid request"}), 400

    #This Microservice runs independently Other microservices can call this service when needed.

    order = {
        "order_id": order_id,
        "product_id": data["product_id"],
        "quantity": data["quantity"],
        "status": "confirmed"
    }

    orders.append(order)
    return jsonify(order), 201

if __name__ == '__main__':
    app.run(port=5002, debug=True)

Advantages of the Microservices Architecture

Flexibility

Each service can be updated independently. This means you can work on one service without affecting the rest of your system—perfect for quick iterations and agile development.

Scalability

Microservices scale horizontally. Instead of making a single skyscraper taller, you add more "skyscrapers" (or instances of individual services) to meet demand. This way, your infrastructure grows as your user base does, allowing for more efficient load distribution.

Easier maintenance

Since services are isolated, fixing bugs or upgrading features in one part of the app doesn’t risk breaking the entire system.

Challenges of microservices

Complexity

Managing microservices requires handling a distributed system with multiple moving parts. You'll need specialized tools and strategies for ensuring that these services communicate effectively, data is synchronized, and deployments are seamless.

Increased overhead

Monitoring, scaling, and maintaining separate services requires more resources and expertise. Microservices can feel like managing an entire city compared to running one skyscraper.

A Quick Comparison of Monolith and Microservices

	Monoliths	Microservices
App size and complexity	If you’re building a small, self-contained app with limited features, a monolithic approach might work best. Keep it simple.	If your app is expected to scale rapidly or handle complex, interconnected features, microservices can offer the flexibility you need for growth.
Team experience	If your team is small or relatively inexperienced, starting with a monolithic architecture might be the best choice. It’s simpler to manage, especially in the early stages.	A more specialized skill set is required to manage microservices. You'll need to invest in infrastructure and tools for deployment, monitoring, and data consistency.
Scalability and future growth	While you can scale a monolith, it becomes challenging as the app grows. Adding more resources to the same codebase can lead to complications in performance and maintenance.	If you anticipate rapid growth or expect your app to adapt quickly to market demands, microservices can scale more effectively and give you the agility to respond to changing requirements.
Speed of development	If your goal is to launch quickly and iterate fast with a minimum viable product (MVP), monolithic architecture is a quicker solution. It’s easier to get started, and you can deploy your app faster.	With microservices, the setup can take longer, but once you have it in place, scaling and iterating becomes easier in the long term.

No one-size-fits-all solution

Choosing between monoliths and microservices architectures isn’t a one-size-fits-all decision. It depends on your app's specific needs, the complexity of your features, and your team’s experience.

As the app grows, there’s always room to evolve your architecture. Many companies start with a monolith and gradually move toward microservices as their needs expand. The key is to make the best choice based on your current situation but always be ready to pivot as your product and team evolve.

In the end, whether you choose monolith or microservices, both architectures have their place in modern software development. Experiment, learn, and choose the approach that best supports your app’s long-term success.