Redirect and render in Ruby on Rails - Performance & Optimization

Performance: Redirect and render

MEDIUM IMPACT

This concept affects page load speed and user experience by controlling how the browser navigates or updates content after a server response.

Updating page content after form submission

Ruby on Rails

def create
  if @item.save
    render :show
  else
    render :new
  end
end

Render updates the current page content without a new HTTP request, speeding up content display.

📈 Performance GainSingle HTTP response, no extra page reload, reduces LCP and improves perceived speed.

Updating page content after form submission

Ruby on Rails

def create
  if @item.save
    redirect_to items_path
  else
    render :new
  end
end

Redirect causes a full new HTTP request and page reload, increasing load time and delaying content display.

📉 Performance CostTriggers 2 HTTP requests and 2 page loads, increasing LCP and blocking rendering longer.

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Redirect	Full DOM rebuild	Multiple reflows due to full reload	High paint cost	[X] Bad
Render	Partial DOM update	Minimal reflows	Lower paint cost	[OK] Good

Rendering Pipeline

Redirect sends a 3xx HTTP status causing the browser to request a new page, triggering full reload and re-render. Render sends HTML directly in the response, updating the current page content without reload.

→Network Request

→HTML Parsing

→Style Calculation

→Layout

→Paint

⚠️ BottleneckNetwork Request and HTML Parsing due to full page reload in redirect

Core Web Vital Affected

LCP

This concept affects page load speed and user experience by controlling how the browser navigates or updates content after a server response.

Optimization Tips

1Use render to update page content without a full reload for better speed.

2Use redirect only when you need to navigate to a different URL.

3Avoid unnecessary redirects to reduce network requests and improve LCP.

Performance Quiz - 3 Questions

Which method causes the browser to make a new HTTP request and reload the page?

A render

B both redirect and render

C redirect

D neither redirect nor render

DevTools: Network

How to check: Open DevTools, go to Network tab, submit form and observe if multiple requests occur or just one response with HTML.

What to look for: Multiple HTTP requests indicate redirect; single HTML response indicates render, which is better for performance.