Ruby, Rails, Jekyll, Sinatra, RubyGems resources

active record
active storage
api clients
api-only apps
assets (JS, images, CSS)
autoloading & constants
background jobs
caching
callbacks
concurrency, parallelism
configuration - routing
controllers
css
data models
datasets
db options
db queries
db schema migrations
db seeds
debugging
deployment - devops
documentation
ecommerce, payments
email
generators & templates
graphics, pdfs, images
internationalization
javascript
logging
metaprogramming
modules
monitoring
ocr
optimization
publishing
rack middleware
rails CLI
rails v6
rails v7
rails websockets (active cable)
revision control
ruby language
ruby language extensions
rubygems
scaffolds
testing
tutorials & resources
validations
views (HTML forms)
views (HTML helpers)
views (layouts & rendering)
visualization
web servers