How bottleneck testing works
September 13, 2023

Bottleneck Testing: What It Is & How It Works

Performance Testing

Performance testing ensures that your system can handle traffic loads without crashing, slowing down, or impacting the user experience. An important part of the process is identifying bottlenecks. This is also known as “bottleneck testing." Bottleneck testing finds system bottlenecks so they can be fixed before impacting performance. In this blog post, we guide you through the process of bottleneck testing, including how it works, tools, and use cases.

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What is a Bottleneck in Software Testing?

A bottleneck is a choke point in your system that reduces or limits throughput, response time, or scalability, resulting in suboptimal performance and a poor user experience. Bottlenecks can impact the system as a whole or only a specific function. For instance, bottlenecks might be slow database queries, memory leaks, network congestion, or inefficient algorithms.

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What is Bottleneck Testing?

Bottleneck testing is a type of performance testing that identifies the weakest link or "bottleneck" in a system, application, or infrastructure, so it can be fixed. A bottleneck is a point in the system where the performance gets constrained, leading to reduced throughput or increased latency. Once a bottleneck is found, DevOps, SREs, IT, developers or other stakeholders can resolve and optimize it, and ensure better performance.

To test for bottlenecks, developers, and testers need to simulate various loads on the system. Then, they monitor KPIs like response time, throughput, error rate, CPU, or memory utilization. By tracking these metrics, they can pinpoint the areas where the system is least efficient and then take corrective action. This could include increasing memory, refactoring code, adding servers, optimizing databases, and more.

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Bottleneck Testing Benefits

Bottleneck testing is recommended because it contributes to the overall performance, reliability, and scalability of the system. Here are some of its primary advantages:

Optimized Performance

By identifying the weakest link in the system and removing the bottleneck that is causing performance degradation, the system runs more efficiently, reliably and robustly, and can more easily scale.

Accelerated Troubleshooting

When performance issues arise, knowing where the bottleneck is can significantly speed up the troubleshooting process. Developers and other engineers can directly investigate the problematic component rather than having to sift through the entire system first, searching for the root cause of the issue.


Knowing exactly where the bottleneck is allows allocating resources more effectively. Instead of wasting time combing through the entire system looking for the error or upgrading the entire system, bottleneck testing ensures resources are invested only where they are needed.

Proactive Problem-Solving

Bottleneck testing helps you identify issues before they become critical. This proactive approach can prevent overarching system failures and the associated downtime, which can be costly and damaging to the company’s reputation, not to mention very painful to fix.

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How Bottleneck Testing Works

When bottleneck testing, developers or testers simulate a load on the system and observe the system's behavior. Metrics like CPU usage, memory consumption, disk I/O, and network latency are closely monitored. Once the bottleneck is identified, the next steps involve optimizing that specific area and then re-testing to ensure the issue has been resolved.

At a high level, the steps of bottleneck testing are:

  1. Define your testing scenario.

  2. Identify your KPIs.

  3. Determine your performance environment.

  4. Select a testing tool.

  5. Run the test.

  6. Collect performance metrics.

  7. It’s time for a bottleneck analysis. Analyze the data - look for anomalies, trends and correlations, compared to the baseline.

  8. Work with stakeholders to resolve the bottlenecks.

  9. Test again to ensure the bottleneck issue has been fixed.

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Tools for Bottleneck Testing

Some of the most common tools for bottleneck testing include:

  • JMeter - An extremely popular open-source load testing tool. JMeter is customizable, flexible and has an easy to use GUI, as well as scripting options.
  • Gatling - An open-source load testing tool that uses a domain-specific language for test scripting, making it easier to write complex scenarios.
  • BlazeMeter - Open-source-based, BlazeMeter enables running JMeter and Gatling scripts in the cloud or enables creating your own script. BlazeMeter helps organizations scale their testing and provides additional features like clear reporting and test data, making it easier to identify bottlenecks.
  • APMs - APM tools can be used for monitoring cloud-based applications in real-time and finding bottlenecks. APMs include New Relic and Dynatrace.
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Bottleneck Testing Use Cases

Bottleneck testing is an effective practice that can be applied across various domains and types of systems. Here are some common use cases where bottleneck testing is recommended:

  • Websites: Ensure that the website can handle ongoing traffic as well as peak traffic during special events.
  • Website Checkout Process: Test the checkout process under load to ensure that transactions are processed efficiently and without errors.
  • Payment Gateways: Ensure that transactions can be processed quickly and securely, even during peak usage times.
  • Data Transfer: Evaluate the system's ability to handle large data payloads.
  • Databases: Identify slow queries or issues with indexing that could affect the performance of applications relying on the database.
  • Cloud Services - Ensure that auto-scaling features work as expected, and that the system can handle spikes in computational load without performance degradation.
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Bottom Line

By performing bottleneck testing early and often, you can identify bottlenecks on time and avoid costly and resource-intensive fixes. Start by building your scenario. Then, choose your tool, analyze the data, optimize and rerun the test. It is also important to understand the greater context of load testing best practices. Get started bottleneck testing today with the industry's most-trusted load testing platform for free today!

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