Scalability Testing For Beginners

Scalability Testing is a non-functional testing method that measures a system’s performance or network when the number of user requests is scaled up or down. The purpose of this testing is to make sure that the system can handle the projected increase in data volume, user traffic, transaction counts frequency, etc. It tests the system able to meet the growing needs.

It is also called performance testing, as it focuses on the application’s behavior when deployed to a system or tested under excess load. Scalability Testing is used to measure how the application stops scaling and identifies the reason behind it.

EXAMPLE: Suppose scalability testing determines the maximum load to be 10,000 users, then for the system to be scalable. In that case, developers need to decrease response time after the 10,000 user limit is reached or increase the RAM size to accommodate the growing user data.

Prerequisites for Scalability Testing

  • Load Distribution Capability-Check whether the load test tool requires several machines to produce the load and manage it from a central point. 
  • Operating System- Verify the load generation agents and the load test master running under what operating systems 
  • Processor- Check the virtual user agent and load test master for what sort of CPU is required 
  • Memory- Check how much memory for the virtual user agent and the load test master will be adequate.

Steps to initiate Scalability Testing

  1. Define the process that is repeatable for executing scalability tests.
  2. Now determine the criteria for scalability.
  3. Now shortlist the software tools required to run the test.
  4. Set the environment and configure the hardware needed to perform the tests.
  5. Plan the test as well as Scalability Tests.
  6. Create and checks the visual script.
  7. Create and demonstrate the load test scenarios.
  8. Execute the tests.
  9. Evaluate the results.
  10. Generate required reports.

Tips for improving scalability

  1. Offload the database by limiting transactions. However, do not go overboard, loading everything into the app layer. You could face other performance issues.
  2. Alter one variable at a time. This is time-consuming, but changing too much at once can make your application’s performance worse.
  3. Reset everything before executing a test to ensure that the tests do not influence your current one. It is recommended to restart the entire software system, but you can leave your hardware running.
  4. Caches can help significantly with offloading resources. Consider implementing a CDN to help take some of your origin server’s load off and place it on the CDN’s servers for even faster performance.
  5. There is no need to store data permanently in the database. Store only necessary data that help to improve your business or application.
  6. Breaking processes into stages and separating them into queues to be executed by a minimal no of workers can give you a performance boost.
  7. Automate the testing process. In this way, you can spend the working hours analyzing the tests that are conducted during off-hours. Automation makes sure that testing and retesting are performed consistently with the same settings.
  8. Restrict access to resources. If you have various requests for the same help that performs the same calculation, let each finish before starting. Otherwise, the process will slow down.
  9. Network communications take more time than in-memory communications, limiting the chatter between your application and your network.


  • It helps in determining the drawbacks of the web application under test in terms of either Network Usage, Response time, CPU Usage, etc.
  • It determines the end-user experience under load. Correct measures should be taken in advance to rectify the problems and make the application more scalable.
  • To reduce the risk of losing money and its goodwill because of an application’s lousy performance, it is crucial to do Scalability testing before releasing it in a production environment.
  • Scalability testing helps in a useful tool utilization tracking.
  • It uncovers the exact cause of several performance issues in an application in the testing phase, saving time and money if detected in the production environment.


  • The use of tools for scalability testing and a specified testing team for performance testing can lead to over budget.
  • Tests that are working fine get failed in the testing phase due to the wrong test, and test scripts lead to a waste of time in making changes.
  • Functional errors cannot be identified in Scalability testing.
  • The test window is very narrow not to disrupt business processes, and hence the defects remain uncovered.
  • Time spent on testing each attribute of Scalability testing is sometimes high and can delay meeting the deadlines of the project.
  • The testing environment is not as same as a production environment and can result in various issues.

Scalability Testing Attributes

  1. Throughput

It is defined as several requests processed per unit time. However, for different applications, the definition of throughput may vary and is tested differently.

  1. Memory Usage

Memory Usage is also tested to get the best results of memory consumption for an application. For less use of memory, good programming practices should be followed by programmers like less use of redundant loops, reduce hits to a database, handling full validations at the client-side only, etc. An application often runs out of memory due to a large number of requests, so developers should always keep an extra database to handle such situations.

  1. CPU Usage

It is tested to check the CPU utilized in performing the task in an application. CPU Usage is measured in MegaHertz. For more throughput and less CPU usage, the code of any application written in any programming language should be properly optimized. 

  1. Network Usage

The bandwidth consumed in performing a task in an application is tested. Network Usage is measured in bytes, segments, packets received or sent per second over the network. For a flawless application to give the best results, network usage should be minimum. 

  1. Response Time

Response time is the time between the response and user request from the application server. It is tested at various loads either by increasing the no of requests per user or increasing the no of users to verify that at what point of time the application will start responding late.

Scalability Test Plan

Create a thorough research schedule before you finally build the experiments. It is an essential step to ensure that the evaluation conforms to the specifications of the application.

  • Steps for Scripts: A thorough step should be taken in the test script to decide the precise actions a person will perform. 
  • Run-Time Data: All run-time data used to communicate with the programme can be decided by the test schedule. 
  • Data drivenTests: If scripts require different data at runtime, all fields that need this data need to be known.

Best Scalability Testing Tools


CyberFlood is a powerful and easy-to-use test solution that generates realistic application traffic and attacks to test your app-aware networking devices and solutions’ performance, scalability, and security. Test and enforce application traffic policies. Benchmark performance and capacity. Validate network security.

Scalability Testing


  • Emulation, Not Simulation. 
  • Broad Capabilities.
  • Encryption.


You need to contact the vendor for the price.

Load Impact

Load Impact is a cloud-based testing system to create their websites, mobile applications, and APIs by performing a series of performance tests indicative of your systems’ stress endurance. 

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  • Possibility to add extra IPs.
  • API testing.
  • Automated and advanced scripting.
  • Browser emulation.
  • Mobile testing 


  • Basic-$89 per month
  • Standard-$299 per month
  • Advanced-$699 per month
  • Pro-$1299 per month


What is scalability testing?

Scalability Testing is a non-functional testing method that measures a system’s performance or network when the number of user requests is scaled up or down. The purpose of this testing is to make sure that the system can handle the projected increase in data volume, user traffic, transaction counts frequency, etc. It tests the system able to meet the growing needs.

Why is there a need for scalability testing?

Scalability testing helps you to determine how your application scales with the increasing workload.
It determines the user limit for the Web application.
It determines client-side degradation and end-user experience under load.
Determines server-side robustness and degradation.

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