Building Scalable Mobile Apps Is Key to Long-Term Product Success

What Is Scalability in App Development?

In simple terms, scalability is your application’s ability to handle a growing user base without affecting the user experience and the app’s performance. That means your applications’ infrastructure needs to be able to support a large number of requests per minute (RPMs). 

Each user interacting with your application generates a request to your backend — the backend should process that request with a minimum delay.  A highly scalable app efficiently manages many requests at once, delivering seamless experiences to users.

Vertical scaling

Vertical scaling adds more resources like CPU, memory, network capacity, and more to the existing application server. It’s powerful enough to handle a large number of simultaneous requests. However, adding resources can be limited depending on the capabilities of existing servers. Because of that, horizontal scaling is the preferred option in many use cases.

Horizontal scaling

Horizontal scaling or scaling out adds more machines or servers with the application code to increase the capacity. The existing resources of the computing instances do not change, but the application logic may need to change to run in parallel. Popular in distributed systems, a load balancer will handle the incoming requests and distribute the load to multiple machines.

It’s not a requirement to use either horizontal or vertical scaling only. But you can have a hybrid system that includes vertically scaled machines in a horizontally scaled system.

How Do You Scale a Mobile App?

Identify the scalability requirements

Before jumping straightaway into scaling a mobile app, you first need to ensure you have a viable reason for it. Your scaling expenses need to match the growing user demand in your app to avoid unnecessary costs. Here are the questions you should answer that will help you decide whether the time to improve capacity has come.

• Do you expect growth in your user base? If yes, how long would it take? Look at the trends in data analytics.
• What is the annual expected number of users of your app?
• How long can your current setup serve the growing user base without losing performance?
• Are there any events or holidays where you observe high demand and heavy usage?
  

By knowing the answers to these questions, you will have a better understanding of where you’re at with capacity and where you need to be to meet the spikes in demand. The information will also help you estimate the budget for scaling your app.

Identify where the scalability issues arise

If you already have an application, discover where scalability issues may occur using application monitoring tools like New Relic AMP and AppDynamics. Using the chosen tracking tool, track key metrics like CPU, memory, and network usage. If any of these metrics show high usages, find out the transactions responsible for them. Take these results as a benchmark to find out where and how to inject scalability.

Choose the right tech stack

Your mobile app’s tech stack is the key to scalable mobile applications. Thus, choosing the right tech stack with a scalable backend and a responsive front-end technology is a must. If your current tech stack doesn’t leave much room for scalability, consider rewriting your app.

An app rewrite will be a significant investment initially, but when you consider a growing user base of satisfied customers, the ROI will follow soon. For example, consider Wallmarts' decision to transition into its legacy system to Node.js. With that decision, they have been able to gain 98% of growth in mobile conversion.

Decide on the right infrastructure

The application’s infrastructure plays a key role in achieving the desired scalability. Using Platform-as-a-Service (PaaS) solutions like AWS, Azure, or IBM Cloud for your mobile app is a great way to meet a variety of scalability needs. Cloud services have many scaling and pricing options.

For example, if you choose to deploy your app in AWS, the vendor will take care of all the necessary scaling demands on your behalf — many renowned cloud services offer auto-scaling where the app dynamically scales according to the current user demand.

You just have to define the required parameters such as how many maximum servers and other resources like storage, middleware, and networking the service should allocate. In addition, you also have the flexibility to change these parameters according to future app usage statistics. Scaling a mobile application that serves millions of users in a PaaS environment is an easy and flexible approach to scalability. 

Use caching wherever possible

Caching is another way you can optimize the code for scalability. When you cache the frequently required data, it’s readily available and users can retrieve it faster. Caching helps significantly reduce the processing time. 

For example, say your mobile app gets data from an API call. If you save the data in a cache, the next time another user requests the same data, the app won’t need to make that API call again since the data is readily available in the cache.

Caching is a highly useful approach to reducing the amount of data processing when the load is high. When you use caching correctly, it can also make the app work in offline mode.

Choose the right architectural pattern

Your app’s architecture can have a big impact on app scalability. For example:

The three-tiered architecture

Client, server, and the application are at different layers where each performs only the most essential tasks. This architecture simplifies each layer, thereby improving scalability and performance.

The microservice architecture

This architecture helps build flexible applications by making individual services loosely coupled with each other. Individual services of a microservice architecture can be scaled to meet the demand.

Scaling databases

If you want to handle a larger number of user requests (e.g., a workload that exceeds the capacity of a single database), you can scale your database horizontally:

• Shard the database into multiple servers or nodes. Sharding helps achieve better read and write performance and reduces the risks of node failures. 
• If the app is in the cloud architecture, add more read replicas for workloads that need heavy read operations.
• Move old information to archives so that the main database can have more space when more read and write operations happen. 

Use Mobile Content Delivery Networks (CDNs)

Mobile CDNs make content delivery faster because CDNs distribute the information from locations closer to the user. The content is delivered in a shorter time. Mobile CDNs are very useful when your mobile apps’ users are distributed across different regions.

Mobile CDNs are developed specifically to operate on mobile networks and deliver content to mobile devices faster.

How Do You Estimate Scalability in Mobile App Development?

Load testing 

A good way to estimate the current scalability of your app is by using load tests. A load test result will tell you how your app performs under a sustained high user load. A load test will show you valuable information such as response times, the server CPU and memory usage, application performance bottlenecks, etc. A highly optimized and scalable app produces a minimum number of violations within the acceptable service level agreements (SLA) for every key transaction under a high user load. 

Performance testing

Performance testing shows your app’s overall performance that includes load and stress testing. Performance testing gives you a better understanding of the app’s performance, stability, and availability.

Scalability testing

Scalability testing is part of performance testing specifically designed to identify the scalability of an app. During such a test, you can measure how the system behaves when the number of requests becomes higher and lower. From this test, you can identify where the application stops responding and the root cause behind it.

What Are the Benefits of Scalability?

Here are the major benefits of having a highly scalable app:

• Help maintain continuous user engagement by delivering an excellent in-app user experience
• Gain a higher return on investment (ROI) through satisfied customers and high retention rates
• Serve a large number of users during spike events (e.g., holidays)
• Grow the application without having to rebuild it from scratch

Scalability Is the Foundation of Successful Digital Products

Scalable mobile applications provide users with a positive UX, which helps your business grow. If your app is scalable enough, you can manage varying user loads with minimum downtimes and without affecting the application’s performance.