Every developer reaches a point where they have to make a big decision. Do I build this as one big application or break it into smaller independent pieces? This choice affects how you write code, how your team works, how you deploy, and how your app grows over time.
There is no universally right answer. But by the end of this article, you will know exactly which one fits your situation.
What Is a Monolith?
A monolith is a single application where all the parts live together in one codebase. The user interface, business logic, and database access are all packaged and deployed as one unit.
When you make a change, you build and deploy the whole thing together.
A simple e-commerce app is a good example. The product listing, shopping cart, payments, and user accounts all live in the same codebase. One app, one deployment, one database.
What a Monolith Looks Like
Everything is in one place. Simple and straightforward.
my-ecommerce-app/ controllers/ models/ services/ views/ database/
What Are Microservices?
Microservices is an architecture where you break your application into small, independent services. Each service does one specific job, runs on its own, and talks to other services through APIs.
Using the same e-commerce example, a microservices version would look like this:
- A Product Service that handles product listings
- A Cart Service that manages shopping carts
- A Payment Service that processes payments
- A User Service that handles accounts and authentication
Each of these runs independently, has its own database, and can be built, deployed, and scaled on its own.
What a Microservices Setup Looks Like
product-service/ cart-service/ payment-service/ user-service/ api-gateway/
How They Are Different
| Monolith | Microservices |
| One single codebase | Multiple separate codebases |
| Deploy everything at once | Deploy each service independently |
| Scale the whole app | Scale only what needs it |
| Direct function calls | API calls between services |
| Usually one shared database | Each service has its own database |
| Simple to start | Complex to manage |
The Case for Monoliths
Monoliths have a bad reputation these days. Many people hear the word and think of old, slow, hard-to-maintain codebases. But that is not always fair.
A well-built monolith is a perfectly good architecture, especially in these situations.
You Are Just Starting Out
When you are building a new product, you do not yet know how it will grow. Starting with a monolith lets you move fast, test ideas, and change things without the overhead of managing multiple services.
Amazon, Twitter, and Shopify all started as monoliths. They only moved to microservices after they grew to a point where the monolith became a problem.
Your Team Is Small
Microservices work best when different teams own different services. If you have a team of two or five developers, splitting into microservices means everyone is jumping between multiple codebases, managing multiple deployments, and dealing with complex inter-service communication. That slows you down more than it helps.
You Want Simple Debugging
In a monolith, when something goes wrong, you look in one place. You have one set of logs, one error trace, and one deployment to check. Debugging across multiple microservices is significantly harder.
You Want Fast Development Early On
With a monolith, a developer can add a feature end-to-end without touching multiple services or coordinating with other teams. This speed is valuable when you are in the early stages of building a product.
The Case for Microservices
Microservices solve real problems, but only at a certain scale. Here is when they start to make sense.
Your App Has Grown Too Big for One Team
When your codebase gets large enough that multiple teams are constantly stepping on each other, changing the same files and breaking each other’s work, it is time to think about splitting things up.
Microservices let each team own one service. They can work, deploy, and scale independently without waiting on anyone else.
Different Parts of Your App Have Different Scaling Needs
In a monolith, if your payment processing is under heavy load, you have to scale the entire application even if everything else is running fine. That wastes resources and costs more money.
With microservices, you scale only the payment service. Everything else stays the same.
You Need High Availability in Specific Areas
If your payment service goes down in a monolith, it can take the whole app with it. With microservices, a failure in one service does not necessarily bring down the others. You can build in resilience at the service level.
Your Teams Are Organised Around Business Functions
Microservices work best when your engineering teams are structured the same way. One team for payments, one for users, one for products. Each team owns their service from development to deployment. This is where microservices truly shine.
The Hidden Costs of Microservices
Microservices sound exciting. Independent deployments, scalability, resilience. But they come with real costs that are easy to underestimate.
Network complexity. In a monolith, your functions call each other directly. In microservices, every call between services goes over a network. Networks fail, slow down, and add latency. You have to handle all of that.
Data management. When each service has its own database, keeping data consistent across services becomes a serious engineering challenge. What happens when the payment service processes a charge but the order service fails to record the order?
Deployment overhead. Instead of deploying one app, you are now deploying five, ten, or twenty. Each needs its own CI/CD pipeline, monitoring, logging, and infrastructure.
Debugging is harder. Tracing a bug across multiple services requires specialised tools like distributed tracing. What used to be one log file is now spread across many services.
More infrastructure. You will likely need an API gateway, a service mesh, container orchestration like Kubernetes, and centralised logging. All of that takes time and expertise to set up and maintain.
So Which One Should You Choose?
Here is a simple way to think about it.
Start with a monolith if:
- You are building something new
- Your team has fewer than ten developers
- You are still figuring out what the product needs to do
- Speed of development matters more than scalability right now
Consider microservices if:
- Your monolith is genuinely slowing your team down
- Different parts of your app need to scale very differently
- You have multiple teams that need to work independently
- You have the infrastructure experience to manage the complexity
A good rule of thumb that many experienced engineers follow is this: start with a monolith, build until it hurts, then break it apart where it makes sense.
The Modular Monolith: A Middle Ground
There is an option that does not get talked about enough. The modular monolith.
A modular monolith is a single application but with very clear internal boundaries. Each feature area is its own module with its own logic and data access. The modules communicate through well-defined interfaces rather than calling each other freely.
This gives you the simplicity of a monolith with the organised structure of microservices. And when the time comes to extract a service, it is much easier because the boundaries are already there.
This is often the smartest starting point for a growing product.
Real World Examples
Netflix runs hundreds of microservices. They process billions of streaming requests daily with different scaling needs for recommendations, video delivery, and billing. Microservices make sense at that scale.
Shopify ran as a monolith for years and only started breaking it apart recently when their scale demanded it. They have spoken publicly about how the monolith served them well for a long time.
Stack Overflow serves millions of developers every day and still runs largely as a monolith. They have optimised it extremely well and it works for their needs.
The lesson is clear. The right architecture depends on your situation, not on what is trending.
Conclusion
Microservices are not automatically better than monoliths. They are a solution to a specific set of problems that come with scale, team size, and complexity.
If you are starting a new project, build a monolith. Keep it clean and well organised. Grow it until it genuinely becomes a problem. Then, and only then, start thinking about breaking it apart.
The best architecture is not the most advanced one. It is the one that helps your team move fast, ship reliably, and solve real problems for your users.