ActiveRecord association loading can use separate queries or joins, and includes may switch between them automatically. preload is the safest default for avoiding surprise eager loading behavior.

Reducing Capistrano deploy time by persisting asset compiler caches across releases can skip repeated Sprockets or Webpacker work. esbuild has no comparable cache directory.

Runtime checks can identify the current RSpec spec type, letting shared setup run only for controller, helper, or request/response-aware examples.

File loading order from Dir.glob can vary by file system and break code that depends on load sequence. Sorting the matched paths or using sort: false in Ruby 3 makes it predictable.

RSpec hook order matters when around(:all) and around(:each) wrap setup and teardown; their execution timing differs from before and after hooks.

Cucumber test suites can hide slow steps that waste most runtime. --format usage measures step durations and highlights optimization candidates, especially when waiting assertions surface previous delays.

Strong secrets for sessions and secret_key_base can be generated from the shell with apg or bin/rails secret.

Large ZIP downloads can start immediately without writing files to disk, using zip_tricks_stream for custom content or zipline for existing attachments.

has_many :through can return duplicate records when multiple join rows point to the same target; :uniq or DISTINCT removes repeated results.

Database-backed RSpec checks for ActiveRecord lifecycle behavior are more reliable than stubs when verifying side effects like automatically creating associated records.

Simple Git configuration for new developers: aliases, rebase defaults, diff tools, and GitLab push shortcuts for a cleaner workflow.

Long pastes in irb 1.2+ can become extremely slow because multiline mode and syntax highlighting add heavy overhead. Disabling multiline restores fast pasting.

ActiveRecord relations can return only primary keys instead of full records, reducing query payload when just record identifiers are needed.

Feature specs can print noisy Puma startup logs when Capybara launches the test server. Setting Capybara.server = :puma, { Silent: true } suppresses the output.

Class definition code that inspects model columns can crash startup when the database is missing or empty, blocking db:create and db:migrate.

Finding a request in staging or production logs often requires searching several servers and archived files; grep or zgrep can query current and zipped logs.

Activated gems can be checked through Gem.loaded_specs, and required libraries can be detected with defined? on a constant they define.

Time comparisons can fail in tests because Ruby keeps subsecond fractions even when the printed values look identical.

Duplicate package versions in Yarn can break shared globals like window.jQuery, leaving plugins such as datepicker unavailable. resolutions can force one version across dependencies.

ES modules are hoisted, so import order in source can differ from execution order and break code that depends on globals like $.

Content Security Policy schützt Webseiten vor XSS, indem der Browser erlaubte Quellen für Skripte, Styles, Bilder und Verbindungen streng einschränkt.