Rails new project generation - Performance & Optimization

Performance: Rails new project generation

MEDIUM IMPACT

This affects the initial load speed and bundle size of a Rails web application by determining which components and assets are included from the start.

Creating a new Rails project with only needed components

Ruby on Rails

rails new myapp --skip-action-mailbox --skip-action-text --skip-active-storage --skip-javascript

Skips unused components, reducing bundle size and asset compilation time, leading to faster initial page load.

📈 Performance GainSaves 500-1000KB in assets, reduces LCP by 200-400ms

Creating a new Rails project with only needed components

Ruby on Rails

rails new myapp

Generates a full Rails app with all default components, including unused JavaScript frameworks, CSS, and Active Storage, increasing bundle size and load time.

📉 Performance CostAdds 1-2MB to initial bundle size, increasing LCP by 300-500ms on slow networks

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Full default Rails project	Moderate (default views and scripts)	Multiple reflows due to larger CSS/JS	Higher paint cost from bigger assets	[X] Bad
Rails project with skipped unused components	Minimal DOM from leaner views	Single reflow from optimized CSS/JS	Lower paint cost due to smaller assets	[OK] Good

Rendering Pipeline

The Rails new project generation determines which assets and code are included in the initial HTML, CSS, and JavaScript sent to the browser. More components mean more files to compile and send, affecting the browser's parsing and rendering speed.

→Network Transfer

→HTML Parsing

→CSSOM Construction

→JavaScript Execution

⚠️ BottleneckNetwork Transfer and JavaScript Execution due to larger asset bundles

Core Web Vital Affected

LCP

This affects the initial load speed and bundle size of a Rails web application by determining which components and assets are included from the start.

Optimization Tips

1Skip unused Rails components to reduce initial asset size.

2Smaller bundles improve Largest Contentful Paint (LCP).

3Avoid including unnecessary JavaScript frameworks at project start.

Performance Quiz - 3 Questions

What is a performance downside of generating a Rails project with all default components?

A It reduces the number of HTTP requests

B It improves JavaScript execution speed

C Larger initial asset size increases page load time

D It decreases CSS complexity

DevTools: Network

How to check: Open DevTools, go to Network tab, reload the page, and observe the size and number of asset files loaded.

What to look for: Look for large JavaScript and CSS files that delay page load; smaller bundles indicate better performance.