// load & performance testing · Leeds & UK
Know how your software will behave before demand finds the limit.
DevStack provides load and performance testing services for websites, applications, APIs and cloud platforms where reliability matters. We reproduce realistic demand, identify what constrains capacity and give you a clear plan before a launch, campaign or busy period puts the system under pressure.
Discuss a performance test- Senior UK engineers
- Real user journeys
- Full-stack diagnosis
- Clear capacity recommendations
Confidence before a critical moment
A system can appear fast and reliable when only a few people are using it. The important question is what happens when hundreds or thousands arrive at once, a large batch starts processing or an operational team needs the platform at the same time.
Load testing replaces assumptions with evidence. It shows how the complete service behaves as demand increases, where response times begin to deteriorate, what fails first and whether the system recovers cleanly.
When performance testing is worth doing
- A major campaign, public launch or seasonal peak will send an unusual number of people to the service.
- The organisation has experienced an outage or slowdown and the original cause is unclear.
- A new application is approaching launch and the team cannot yet state its safe capacity.
- A migration, upgrade or architectural change may have altered performance.
- Infrastructure costs are rising and you need evidence before scaling further.
- An important internal or mobile workflow must remain usable when the whole operation is active.
- A supplier has said the platform will scale, but the business needs independent assurance.
What we can test
We shape the test around the service and the decision you need to make. That may include a public website, customer portal, SaaS product, mobile application, API, database-heavy workflow or a platform connected to several external services.
The service is not tied to one hosting provider or development stack. We can test applications hosted in AWS, Azure, other cloud environments or private infrastructure, including systems built with Node.js, .NET and other common web technologies.
Types of performance test
Load testing
Checks whether the service remains responsive and stable at expected and peak demand.
Stress testing
Increases demand beyond the expected range to find the limit, understand failure behaviour and see how the system recovers.
Spike testing
Introduces a sudden burst of traffic or transactions to test queues, scaling, databases and recovery.
Soak testing
Runs sustained demand for longer periods to reveal gradual degradation, resource exhaustion and memory or connection problems.
Capacity and scalability testing
Establishes a defensible operating range and shows whether additional infrastructure creates useful capacity or merely moves the bottleneck.
A realistic test, not artificial traffic
A useful test is built around how the system is actually used. We analyse available traffic data, logs and operational patterns, then model complete journeys with realistic pacing, user mixes and demand profiles.
The test might include signing in, searching, submitting forms, creating transactions, calling APIs, processing a batch or using operational screens. We agree the expected peak, the extreme scenario and the point at which the test should stop safely.
How we work
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Understand the risk
Clarify the business event, critical journeys, previous incidents, performance expectations and the decision the test must support.
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Build the workload model
Use analytics, logs and operational evidence to define normal demand, recorded peaks, expected growth and sudden bursts.
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Prepare a safe environment
Confirm that production cannot receive test traffic, protect customer data and isolate payment, email and other third-party services where necessary.
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Run in controlled steps
Start below expected demand, check the evidence and increase load gradually. This reveals where behaviour changes without wasting time or creating avoidable risk.
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Diagnose the constraint
Match client-side response times and errors with application, database, infrastructure and log evidence to identify the actual bottleneck.
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Report the decision
Explain the safe operating range, failure point, likely cause, immediate precautions and prioritised technical changes in plain English.
What you receive
- A documented test scope, assumptions and workload model.
- Reusable load test scripts for the agreed journeys.
- Results for response time, throughput, errors and stability at each level of demand.
- Application and infrastructure evidence showing where capacity is constrained.
- A clear statement of what the system handled and where it began to degrade.
- Prioritised recommendations covering code, database, hosting, monitoring and operating procedures.
- A senior walkthrough for technical and business stakeholders.
We find the cause, not only the symptom
A graph showing slow responses is not enough. Because DevStack is a software engineering company, we can follow the evidence through the application, database, integrations and cloud environment. That helps distinguish between a system that needs more capacity, a query that reads far too much data, a synchronous process that should run in the background or an external dependency that needs different handling.
The result is a practical engineering decision, not a bundle of test output that someone else must interpret.
Independent testing, with help available afterwards
We can test software built by your internal team, another supplier or DevStack. The report stands on its own and there is no obligation to appoint us for remediation. If you want help implementing or retesting the recommendations, the same senior team can remain involved.
Why DevStack
Senior engineers from the start
Every DevStack engineer has more than 15 years of commercial experience. The people designing the test are responsible for interpreting the result.
UK delivery with no offshore hand-off
You work directly with the Leeds-based team carrying out the engagement. Testing and analysis are not passed to a junior offshore team.
Commercially grounded
We begin with the event, risk and decision that matter to the organisation, then test the smallest set of scenarios needed to answer them responsibly.
Able to support the fix
If the evidence points to application code, data access, integrations or infrastructure, we can help your team understand and resolve it.
Recent work
For a UK organisation relying on a cloud platform during periods of concentrated demand, DevStack built a safe performance test mode, reproduced complete user and operational journeys and tested the platform at multiples of its recorded peak.
The work proved normal capacity, found the exact database limit under an extreme burst and exposed a separate data-access bottleneck in an operational workflow. The organisation received a clear capacity plan, monitoring recommendations and prioritised code changes.
Read the anonymised load testing case study →Load and performance testing in Leeds and across the UK
DevStack is based in Leeds and works with organisations across Yorkshire and the UK. We can run discovery and stakeholder sessions in person for local teams, with test execution and monitoring handled remotely where appropriate.
Frequently asked questions
What is the difference between load and performance testing?
Performance testing is the wider discipline. Load testing is one method within it, focused on behaviour at expected or increasing demand. A performance engagement may also include stress, spike, soak and capacity testing.
Can you test our production website?
We normally recommend a representative, isolated test environment. Generating heavy traffic against production can affect real users and connected services. Where a limited production test is justified, it requires explicit approval, safeguards and a carefully controlled scope.
What happens to payment, email and other external services?
We identify every external call before testing. Services that could create charges, send messages, consume credits or affect third parties are normally replaced, disabled or isolated in the test environment.
Which hosting platforms and technology stacks can you test?
The application can be hosted in AWS, Azure, another cloud, on premises or through a third-party provider. We can test Node.js, .NET and other common web application stacks. The architecture, available monitoring and test environment shape the approach.
Which tools do you use?
We select tools to suit the system and environment. Our work can include Apache JMeter, k6, cloud-based load generators, application monitoring, platform metrics and custom diagnostics. The commercial question and quality of the workload model matter more than the name of the tool.
How long does a performance testing engagement take?
A focused engagement often takes two to four weeks once access, data and a suitable environment are available. A connected platform with several journeys or extensive preparation may take longer. We confirm the plan before work begins.
Can you fix the problems you find?
Yes, if that is useful. The report is independent and can be handed to your existing team or supplier. DevStack can also implement targeted improvements and repeat the tests to confirm the result.
How much does load testing cost?
Cost depends on the number and complexity of journeys, preparation required, test scale, environment, monitoring access and whether retesting is included. After an initial call, we provide a defined scope and estimate.