The beginner's guide to performance testing

Foundations

What performance testing is, why speed matters to a business, and what a first load test looks like.

1. Part 2 What is website performance, and why does speed matter? Why is website speed important? What website performance really covers, what slow pages cost in conversions and rankings, and how performance is measured.
2. Part 3 The types of performance testing, and when to use each The types of performance testing explained for beginners: load, stress, spike and soak, plus smoke, capacity, volume and scalability, and which to run when.
3. Part 4 What is a virtual user? A virtual user is a simulated visitor in a load test. What VUs actually simulate, how they differ from concurrent users and requests, and the traps to avoid.
4. Part 6 How to load test a website: your first test, step by step How to do load testing on a website for the first time. Ten steps, from choosing one journey and sizing it from real traffic to reading the final report.

How a web page loads

The journey from a typed URL to a rendered page: DNS, TLS, the first byte, caches, scripts and images, and why mobile is slower.

1. Part 8 What happens when a web page loads: DNS, TLS, TTFB and render How does a web page load? Seven waits, from DNS lookup and TLS handshake to first byte and render, with what each costs and which grow when a site is busy.

Measuring speed

Core Web Vitals and the metrics around them, the tools that report them, and how to read a score without being misled by it.

Parts in this module are still to come.

Load-testing vocabulary

Virtual users, concurrency, throughput, ramp-up and the other words every load test report uses.

1. Part 7 How many concurrent users can my website handle? (with calculator) Concurrent users are the people on your site at the same moment. The formula, a worksheet calculator, a lookup table, and why capacity must be measured.

Types of tests

Capacity, volume, scalability and the rest of the testing family, and which shape of test answers which question.

1. Part 5 What is capacity testing? Capacity testing finds how many users your site can serve while still meeting its speed targets. How it differs from stress testing, and how to run one.

Running tests safely

Sizing, duration, environments, test data, pass criteria and the operational blockers every first test hits.

Parts in this module are still to come.

Reading results

Reading a report, spotting results that will not survive production, and explaining the numbers to the people who fund the fix.

Parts in this module are still to come.

Where slowness comes from

Where sites actually slow down under load: databases, caches, third-party services, autoscaling limits and queues.

Parts in this module are still to come.

Ecommerce and peak season

Peak-season readiness for online stores: Black Friday planning, flash sales, checkout and platform-specific slowdowns.

1. Part 1 How to prepare your website for Black Friday: the 12-week plan Black Friday website preparation as a 12-week countdown: size your peak from last year, load test early, fix, rehearse the spike, freeze, and stand watch.

Tools and capstone

Choosing and comparing tools, plus the reference material that ties the guide together.

Parts in this module are still to come.