Heroku deployment in Ruby on Rails - Performance & Optimization

Performance: Heroku deployment

MEDIUM IMPACT

This affects the initial page load speed and server response time by how the app is deployed and served on Heroku.

Deploying a Rails app on Heroku for fast user access

Ruby on Rails

Procfile:
web: bundle exec puma -C config/puma.rb

# Use Heroku Ruby buildpack and optimized Puma config

Using Puma with optimized config and specifying it in Procfile improves concurrency and startup speed.

📈 Performance Gainreduces server startup time, lowers LCP by seconds

Deploying a Rails app on Heroku for fast user access

Ruby on Rails

git push heroku master
# No buildpacks or Procfile configured, default web server used

Using default settings without specifying a proper web server or buildpacks can cause slow startup and poor request handling.

📉 Performance Costblocks initial response for several seconds, increasing LCP

Performance Comparison

Pattern	Server Response	Asset Delivery	Startup Time	Verdict
Default Heroku deploy without Procfile	Slow (5+ sec)	Direct from dyno	High (cold start)	[X] Bad
Heroku deploy with Puma and Procfile	Fast (1-2 sec)	Precompiled + CDN	Low (warm dyno)	[OK] Good

Rendering Pipeline

Heroku deployment affects the server response stage before the browser starts rendering. Slow server response delays Style Calculation and Paint.

→Server Response

→Style Calculation

→Layout

→Paint

⚠️ BottleneckServer Response time due to dyno startup and request handling

Core Web Vital Affected

LCP

This affects the initial page load speed and server response time by how the app is deployed and served on Heroku.

Optimization Tips

1Always specify a Procfile with an optimized web server like Puma for Heroku Rails apps.

2Precompile assets before deployment and use a CDN to speed up asset delivery.

3Monitor server response times to reduce Largest Contentful Paint (LCP) delays.

Performance Quiz - 3 Questions

What Heroku deployment practice improves server response time for a Rails app?

A Deploying without precompiling assets

B Using default WEBrick server

C Using a Procfile with Puma web server

D Serving assets directly from dyno without CDN

DevTools: Network

How to check: Open DevTools > Network tab, reload page, check Time to First Byte (TTFB) and asset load times

What to look for: Low TTFB indicates fast server response; fast asset load times show good asset delivery

Practice

1. What is the main purpose of deploying a Rails app to Heroku?

easy

A. To put the app online without managing servers

B. To write Ruby code faster

C. To create a local database

D. To debug Rails code automatically

Solution

1. Step 1: Understand Heroku's role

   Heroku is a platform that hosts apps so they can be accessed online without you managing the servers.

2. Step 2: Compare options

   Options B, C, and D describe development or debugging tasks, not deployment.

3. Final Answer:

   To put the app online without managing servers -> Option A

4. Quick Check:

   Heroku deployment = online app hosting [OK]

Hint: Heroku hosts apps online, no server setup needed [OK]

Common Mistakes:

• Confusing deployment with coding or debugging
• Thinking Heroku manages local databases
• Assuming Heroku speeds up writing code

2. Which command is used to push your Rails app code to Heroku?

easy

A. heroku push

B. heroku deploy app

C. rails deploy

D. git push heroku main

Solution

1. Step 1: Identify the correct git command

   Heroku uses git to receive code. The correct command is 'git push heroku main' to push the main branch.

2. Step 2: Check other options

   Options A, C, and D are not valid commands for pushing code to Heroku.

3. Final Answer:

   git push heroku main -> Option D

4. Quick Check:

   Push code with git push heroku main [OK]

Hint: Use git push heroku main to deploy code [OK]

Common Mistakes:

• Using 'heroku push' which is invalid
• Trying 'rails deploy' which doesn't exist
• Confusing Heroku CLI commands

3. After pushing your Rails app to Heroku, which command runs database migrations on Heroku?

medium

A. heroku run rails db:migrate

B. rails db:migrate

C. git migrate heroku

D. heroku migrate db

Solution

1. Step 1: Understand migration on Heroku

   To run migrations on Heroku's remote server, you use 'heroku run rails db:migrate'.

2. Step 2: Check other commands

   'rails db:migrate' runs locally, 'git migrate heroku' and 'heroku migrate db' are invalid commands.

3. Final Answer:

   heroku run rails db:migrate -> Option A

4. Quick Check:

   Run migrations remotely with heroku run rails db:migrate [OK]

Hint: Run migrations remotely with heroku run rails db:migrate [OK]

Common Mistakes:

• Running migrations locally instead of on Heroku
• Using invalid git commands for migration
• Confusing command order

4. You pushed your Rails app to Heroku but see an error when opening the app URL. What is a common cause?

medium

A. You did not install Ruby locally

B. You used 'git push origin main' instead of 'git push heroku main'

C. You forgot to run database migrations on Heroku

D. You opened the wrong browser

Solution

1. Step 1: Identify common deployment errors

   Forgetting to run migrations on Heroku often causes errors because the database schema is not updated.

2. Step 2: Evaluate other options

   You used 'git push origin main' instead of 'git push heroku main' means code wasn't pushed to Heroku, but question says code was pushed. Options A and D are unrelated to deployment errors.

3. Final Answer:

   You forgot to run database migrations on Heroku -> Option C

4. Quick Check:

   Missing migrations cause app errors on Heroku [OK]

Hint: Run migrations after push to avoid errors [OK]

Common Mistakes:

• Ignoring migrations after deployment
• Confusing git push origin with heroku
• Blaming local environment for Heroku errors

5. You want to deploy a Rails app with environment variables for API keys on Heroku. Which is the correct way to set them before deployment?

hard

A. Add keys to config/application.rb file

B. Use 'heroku config:set KEY=value' command

C. Store keys in a local .env file only

D. Push keys directly in your code files

Solution

1. Step 1: Understand environment variables on Heroku

   Heroku uses 'heroku config:set' to securely store environment variables like API keys.

2. Step 2: Evaluate other options

   Adding keys to config/application.rb or pushing keys in code risks exposure. Local .env files are not sent to Heroku.

3. Final Answer:

   Use 'heroku config:set KEY=value' command -> Option B

4. Quick Check:

   Set env vars securely with heroku config:set [OK]

Hint: Use heroku config:set to add env variables securely [OK]

Common Mistakes:

• Hardcoding keys in code risking leaks
• Relying on local .env files for Heroku
• Editing config/application.rb for secrets