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Which Scalability approach is right for our Application? | System Design

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In today’s digital world, the success of an application often depends on its ability to grow smoothly as more users come on board. This is where scalability comes into play. Scalability means making sure your app can handle more users and data without slowing down or crashing. But how do you choose the best way to make your app scalable? In this article, we’ll break it down into simple terms.



Scalability, in simple terms, means your app’s ability to handle more and more users or data without breaking a sweat. Think of it as making sure your car runs just as smoothly with one passenger as it does with a full load.

Different Ways to Make Your Application Scalable

1. Make It Bigger (Vertical Scaling):

This is like giving your car a bigger engine. You’re adding more power to the same vehicle. In tech terms, you boost your server’s capacity with more CPU, memory, or storage. It’s good for smaller apps, but it has limits because you can’t infinitely upgrade hardware.

2. Get More Cars (Horizontal Scaling):

Imagine you have a fleet of cars, and they all share the load. This is what horizontal scaling does. You add more servers or instances to your app, spreading the workaround. It’s great for big apps with lots of users, and it keeps things running smoothly.

3. Divide and Conquer (Microservices):

Think of your app as a puzzle, and each piece of the puzzle is a separate service. Microservices break your app into these pieces, and you can scale up only the parts that need it. It’s like upgrading one section of a highway that’s congested, instead of the entire road.

4. No Servers, No Problems (Serverless):

Imagine you don’t have to worry about maintaining your car at all; it just works when you need it. That’s what serverless does for your app. It automatically handles the scaling for you. It’s cost-efficient and great for unpredictable workloads.

What Influences Your Choice for choosing the correct method of scalability?

Now, let’s talk about what makes you choose one way over the other:

1. How Your App Is Built (Architecture)

If your app is like a big building with everything inside, vertical scaling might work at first. But if it’s more like a city with many different parts, horizontal scaling makes more sense.

2. Picking the Right Database

Databases are like your app’s memory. Some databases are good at handling lots of data and users at once (NoSQL), while others are better for smaller apps (SQL).

3. Counting Your Coins

Money matters! Vertical scaling can be costly because you’re upgrading hardware. Horizontal scaling is usually cheaper in the long run.

4. Staying Safe

If your app needs a lot of security, vertical scaling might be safer because you have more control over a single server. It’s like having one locked door instead of many.

5. Time is the Essence

If your app needs to be super fast (like video calls or games), you want horizontal scaling. It puts your app closer to your users, reducing delay.

6. Up and Down Traffic

If your app’s traffic goes up and down a lot (like a shopping app during holidays), serverless can save you money by only using resources when needed.

7. Technology Stack

he choice of technology stack can impact scalability options. Some technologies are more suited to horizontal scaling, such as container orchestration platforms like Kubernetes, while others may be more aligned with vertical scaling, like traditional monolithic applications.

Making the Right Choice

So, when do you use which method? Here are some scenarios:

Small and Steady

If your application isn’t expected to experience rapid growth in terms of user traffic and resource demands then choose Vertical Scaling because:

  • Vertical scaling involves increasing the capacity of a single server, such as adding more CPU, RAM, or storage to handle increased loads.
  • It is often simpler and requires fewer changes to your application architecture compared to horizontal scaling.
  • Suitable for small-scale applications that don’t need to handle a large number of concurrent users.

Going Big

If you expect a high increase in user traffic and need to ensure your application can handle it, go for Horizontal Scaling, especially if your app is divided into pieces (microservices) because:

  • Horizontal scaling involves adding more servers or instances to your infrastructure, distributing the load across multiple machines.
  • It offers better scalability as you can continue to add more servers as your user base grows.
  • Particularly effective for applications that are designed as microservices, allowing you to scale each service independently.

Variable Loads

For applications with unpredictable traffic patterns or infrequent bursts of activity, serverless can be a good option because:

  • Serverless computing automatically manages the scaling of resources based on demand, making it ideal for variable workloads.
  • You only pay for the actual resources used, which can be cost-effective when your application has idle periods.
  • Serverless platforms, such as AWS Lambda or Azure Functions, handle the underlying infrastructure, reducing operational overhead.

Need for Speed

When your application needs to provide low-latency responses and high performance, horizontal scaling is the good option because:

  • Horizontal scaling allows you to distribute traffic across multiple servers, reducing the load on each server and improving response times.
  • Load balancing techniques can further optimize the distribution of requests for improved speed.
  • Useful for applications where responsiveness and speed are critical, such as real-time systems or gaming applications.

Money Matters

When you have budget constraints but still need to ensure reliability and performance, horizontal scaling is usually the more cost-effective choice because:

  • Horizontal scaling can be cost-effective because you can start with a small number of servers and gradually add more as your application grows.
  • It allows you to optimize resource allocation and reduce costs by scaling up or down based on actual demand.
  • Cloud providers often offer pricing models that align well with horizontal scaling, making it a financially sound choice.

How to Test Your App’s Scalability?

Testing is like taking your car for a spin to make sure it runs smoothly. Here’s how to do it:

  • Load Testing: Use special tools to pretend lots of people are using your app at once. Watch how your app handles it – you want it to stay fast and error-free.
  • Stress Testing: Push your app to its limits. How many users can it handle before things start breaking? Find out where it breaks and why.
  • Adding More Cars: If you’re using horizontal scaling, make sure your load balancer can distribute work evenly between your servers.
  • Checking the Engine (Database): Test how your database handles lots of data. Make sure it can read and write quickly without errors.
  • Fail on Purpose: Simulate things going wrong, like a server crashing. See if your app can handle it and recover gracefully.
  • Keep an Eye Out: After your app is live, use monitoring tools to watch its performance in real-time. Fix any issues that pop up.


Making your app scalable is a smart move in today’s tech world. But it’s not a one-size-fits-all decision. You have to think about how your app is built, how much money you have, and what your users need. Test it out to make sure it works under pressure. Remember, scalability isn’t a one-time thing – it’s an ongoing process to keep your app running smoothly as it grows.

Last Updated : 11 Oct, 2023
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