psi-weekly-cron-baseline

PSI Weekly Cron Baseline

Overview

Automates Google PageSpeed Insights v5 tracking for a configurable list of URLs. Runs on a cron schedule (launchd on macOS, systemd timers on Linux, or GitHub Actions for cloud-ready setup). Stores each run as a row in an NDJSON file for easy historical analysis. Optional regression detection compares current run to N-week average and alerts when scores drop > threshold.

Why: PSI single-shot tells you the current state. PSI over time tells you whether your optimizations stuck — and catches regressions from theme updates, plugin installs, or third-party-script bloat before customers notice.

When to use

• After a performance optimization sprint — verify it stays optimized
• Set up on a site you're consulting — get a 12-week baseline before recommendations
• E-commerce shop using lots of plugins — catch each plugin's perf impact
• Any site where Core Web Vitals are critical to revenue

Don't use for:

• One-shot audits (use seo-audit-free instead)
• Sites with <5 critical URLs (manual checking is fine)
• Internal/staging sites (PSI can't reach them — use Lighthouse CLI locally)

Architecture choices

digraph arch {
    "Where does the cron run?" [shape=diamond];
    "launchd (macOS)" [shape=box,fillcolor=lightgreen,style=filled];
    "systemd (Linux)" [shape=box,fillcolor=lightgreen,style=filled];
    "GitHub Actions (cloud)" [shape=box,fillcolor=lightblue,style=filled];
    "AWS Lambda + EventBridge" [shape=box,fillcolor=lightyellow,style=filled];

    "Where does the cron run?" -> "launchd (macOS)" [label="dev machine, simple"];
    "Where does the cron run?" -> "systemd (Linux)" [label="server, simple"];
    "Where does the cron run?" -> "GitHub Actions (cloud)" [label="prod, team-shared, auditable"];
    "Where does the cron run?" -> "AWS Lambda + EventBridge" [label="needs HA + alerting"];
}

Recommendation: start with launchd locally to validate. Migrate to GitHub Actions for team-shared / production use. AWS Lambda only if you need true 24/7 reliability beyond your local machine's uptime.