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Guides

Start here for definitions, process, and how performance testing fits a release cycle.

The guides are the long-form spine of the blog. If you are new to the subject, Performance testing: the complete guide covers the vocabulary, the test types and the process end to end, and What is load testing? and What is a virtual user? fill in the two terms every conversation with a vendor turns on. What is website performance, and why does speed matter? is the one to send to a stakeholder who asks why any of this deserves budget.

Two guides are about how the work fits a team. Where does performance testing fit in an agile release cycle? looks at when in a sprint the testing should happen and what it should gate, and Playwright for performance testing answers the question engineers ask once Playwright is already in the repo: can it drive virtual users, and where does it stop.

If you would rather follow a sequence, the beginner's guide publishes two parts a week, from first principles through to running and reading your own tests.

Response time chart for the same checkout: at one user the page answers in under a second; as concurrent users approach 3,000 the curve bends and the same page takes eight seconds. Load testing measures that curve before real traffic does.

What is load testing?

Load testing tells you what happens to your site when real traffic shows up at once. This guide explains what it is, why slow pages cost conversions, how a test actually runs, and how to size your first run, with no prior testing background assumed.

Ahmad Farzan ·

The cost of one virtual user. A protocol virtual user in a load tool like k6 costs about 1 to 5 megabytes, so one machine runs tens of thousands of them, shown as a dense field of dots. A real-browser virtual user driven by Playwright costs hundreds of megabytes and about one CPU core, so one machine runs only dozens to low hundreds, shown as a few browser windows. Roughly 50 to 100 times more compute per user.

Playwright for performance testing: can a browser automation tool drive virtual users?

You already know Playwright for end-to-end tests. Can you reuse it for performance testing and call each browser a virtual user? You can, but a real browser is expensive to run, so it drives a handful, not a flood. Here is how far Playwright scales, and where you reach for a different tool.

Ahmad Farzan ·

A release cycle drawn as five stages from planning to production. The weight of each performance test grows from light checks on every commit to a heavy real-browser load test at the pre-release gate, then tapers to monitoring in production.

Where does performance testing fit in an agile release cycle?

Agile teams ship every week, sometimes every day. Performance testing built for a quarterly release does not fit that rhythm, so it slides to the end, then to never, until production buckles. It does not have to. This guide maps each performance test to a stage: cheap checks every commit, a real-browser load test at the pre-release gate, monitoring after.

Ahmad Farzan ·

A performance test timeline. The server answers in 0.28 seconds, but the page is not usable until 4.3 seconds under load, well past Google's 2.5-second LCP budget. The gap is everything the browser does after the server responds: rendering, JavaScript, and third-party tags.

Performance testing: the complete guide

Your server can answer in 50 milliseconds and still ship an eight-second page. Performance testing measures both backend behavior and the browser-rendered experience under controlled load. This guide maps the whole discipline: the types, the metrics that matter, the process, and how to choose between protocol-level and real-browser tools.

Ahmad Farzan ·