Beginner's Guide to Build Scalable Apps

Beginner's Guide to Build Scalable Apps

Hello friends! Recently, I read a detailed and lengthy article by Google on patterns for scalable and resilient apps. So I decide to write an article to summarize and share what I've learned. Please read the full article if you have time because this is just a summary.

What is Scalability?

According to Google,

Scalability is the measure of a system's ability to handle varying amounts of work by adding or removing resources from the system.


In simple terms, it means that an app should be designed in order to handle and support the volatile user traffic. A scalable app is flexible in its ability to adjust to peaks and dips in user traffic. It is also highly resourceful, being able to minimize costs while maintaining good user experience even during periods of high traffic.

Why is it important?

Apps that are built with a scalable design enjoy the following benefits:

  • Maintain continuous user experience regardless of traffic
  • Resilient at all levels of architecture and resistant to failures/outages
  • Optimize costs and resource consumption

Apps with a scalable design focuses on the long term sustainability of its lifecycle. It follows the principles of scalable architecture, which defines what a reliable and resilient app needs in order to be scalable.

Principles of Scalable Architecture

1. Continuous availability

A crucial scalability principle is to ensure that the app is continuously available and accessible to the users once it is launched. Any time a website or app is down, it can be detrimental to the traffic and business.

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This is because availability is a key metric to measuring an app's overall health and resistance to failure. Achieving high and continuous availability maximize the user experience and improve the app's reputation. There are a few ways to ensure continuous availability:

  • Using cloud storage solutions
  • Distributing resources
  • Load balancers (more on this later)

2. Automation

Integrating a DevOps culture with automated pipelines to ensure continuous integration and delivery is a fundamental principle to having a scalable app. Adopting DevOps techniques and practices can improve the quality and reliability of the software.


For detailed information about DevOps and how to get started using a CI/CD tool, please check out Introduction to DevOps.

3. Loose Coupling

Increasing the app's flexibility can be done by breaking your app into several independent services. This type of system design is called loose coupling. A loosely coupled design can reduce the risk of application failure and shutdown, as one error in a component will not majorly affect the entire app. It also allows each component to be managed and deployed individually.

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Another benefit of implementing this design is that each component may have different scaling profiles and requirements. Hence, having independent components and autonomous systems will allow greater flexibility and resilience for the app.

4. Data-Driven Design

Monitoring and measuring key metrics of your app is one of the most important scalability principles. In order to decide how to improve the app's scalability, it is essential to understand the app's behaviour through consistent monitoring and analyzing of relevant metrics. Having access to this data can help assess and detect certain underlying issues in the app.


In addition, gathering data and collecting key metrics can capture information about the app's overall health and performance. This results in improving traffic and user experience.

The Scalability Checklist

Now that you have an idea about the principles of scalability, let's have a few points that we can implement immediately to increase our app's scalability. This is a mini checklist I put together to get started. Of course, I recommend you reading more on your own to adopt more scalable practices for your app.

1. Use modern app frameworks/services

Keep your app up-to-date by using modern frameworks like Node.js. It enhances the app's performance and maintains continuous availability for users. Choose a reputable cloud storage service such as Google Cloud or AWS to store app data.

2. Caches

Caching serves to improve the speed of data retrieval by keeping frequent queries stored for quick access and reducing the reliance of disk-based storage. It also supports the app by keeping storage free for essential data and reducing load on services such as databases to handle more requests at a time.

3. Indexers

Indexing, just like caching, helps improve data retrieval efficiency. Indexing can quickly find a small piece of information from a large dataset, even when it is stored in physically distributed locations.

4. Load balancers

Implementing load balancers helps distribute traffic to different resources. This prevents independent resources to be idle while some are overloaded. Load balancers provide health-checking features, making sure that load will not be distributed to resources that are overloaded or have reached capacity.


It's common to distribute loads to different regions and implement caches strategies to each resource in the system. This keeps the app stable during high traffic and therefore ensures high quality user experience as the app scales.

5. Asynchronous Queues

As your app grows its user base, there will an increasing number of requests to write and process. This could impact the speed of the app and reduce its performance. A solution to this issue would be to perform asynchronous queries by queuing them. Instead of making the client wait for the request to process, the app can receive the request and inform the client. In the meantime, the client can do numerous tasks while waiting for the response.

What's Next

And that's a brief summary of scalability principles to build resilient and scalable apps. I hope you find this article insightful so please leave a like if it is. Designing your app to scalable is a must if you want it to be sustainable for a long time. If you want to read more about this topic, I recommend the articles below to get started:

Thanks for reading! Please share any thoughts below. Cheers!


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