Page speed watcher
A small system that measures a short list of important pages on a fixed device and network profile, several times a run, and reports a regression only when it is larger than the noise. It names the resource that changed, and it never blocks a deploy. Seven posts on the same system — one diagram at a time — with a cost breakdown and an engineering reference at the end.
- 01
A page speed watcher on AWS for a few dollars a month
The whole system on one page — a measurer, a comparer and a reporter — and the reason it takes several samples: one measurement of a web page tells you almost nothing.
- 02
How a page gets measured
The device profile that must never change, how many samples is enough, and the four things that quietly make two runs incomparable.
- 03
How a speed regression is detected
Comparing against a page’s own rolling spread rather than a fixed threshold, why the baseline rolls, and the slow drift no single comparison will ever catch.
- 04
How a performance budget is set
Where a fixed threshold genuinely belongs, why budgeting bytes beats budgeting seconds, and why a budget is a prompt for a conversation rather than a gate.
- 05
How the speed report reads
Naming the resource rather than the metric, correlating a regression to a deploy, and the two numbers worth putting in front of anybody who is not an engineer.
- 06
What the page speed watcher costs
About $12 a month. One Bedrock read per page load is the only line that grows; the queue, the table, the mail and the storage are rounding errors. Plus the three ways the bill could surprise you.
- 07
Engineering reference: the page speed watcher architecture
Same system, drawn purely for engineers. Service names, region, Lambda inventory, IAM scopes, the schemas and the exact model id.
Frequently asked questions
- What is a page speed watcher?
- A small serverless system that measures a fixed list of pages on a fixed device profile several times a run, compares against a rolling baseline, and reports a regression when the change is bigger than the measurement noise. It names what got heavier and does not block anything.
- Why not just use a hosted speed tool?
- Plenty are good and this is a build-or-buy decision. What a small custom one gives you is your own page list, a baseline drawn from your own site rather than a global percentile, and enough runs per measurement to distinguish a regression from noise — which is the thing most tools get wrong.
- Does it fail a build?
- No. A page speed number is noisy enough that gating deploys on it produces false failures, and a check that fails wrongly gets bypassed within a month. It reports after the fact, with the deploy it correlates to.
- What device profile does it use?
- One you choose and never change: a mid-range mobile on a throttled connection is the usual answer. The absolute number matters far less than measuring the same thing every time.
- What does it cost to run?
- A few dollars a month for a handful of pages measured daily. See part six.