rails_performance adds low-effort performance monitoring for Rails apps, surfacing slow endpoints, request timing, query breakdowns, and custom events with Redis-backed dashboards.

CarrierWave defaults often need project-specific tweaks for storage paths, cache cleanup, test isolation, and large-file handling.

Multi-tenant Rails apps can use one OmniAuth setup for several SAML identity providers, loading the right configuration at runtime for secure SSO.

Chrome password leak detection can interrupt Selenium runs with breach warnings on weak or reused credentials. Disabling profile.password_manager_leak_detection suppresses the dialog in automated tests.

Local development can use Passenger Standalone as a zero-configuration Ruby app server with SSL and production-like behavior, replacing Webrick or Thin.

Ruby gems need manual file loading, multi-version support, and their own release workflow, unlike Rails apps. Safe changes depend on understanding structure, tests, versioning, and packaging.

Image descriptions need different wording depending on context: alt text should stay functional, while figcaption can be editorial or illustrative.

Dummy development data is faster to create by reusing FactoryBot factories than by using the UI or Rails console records. Defaults, associations, traits, and attribute overrides come along automatically.

Tiny scripts provide quick web performance metrics for Core Web Vitals, loading, scripts, images, fonts, and interactions.

Selenium tests can fail when pending AJAX calls are aborted as Capybara closes the browser tab. Blocking new requests and waiting for in-flight work reduces flaky teardown errors.

Dependency licenses can break closed-source projects when unapproved OSS terms slip in. License Finder validates all dependencies during test runs and flags restricted licenses early.

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

Rails model validation tests can be written directly with record.validate and error checks, or shortened with shoulda-matchers for standard cases.

Live CSS custom properties cascade through the DOM and can be reused in other values, enabling flexible theming and Web Component styling.

CarrierWave RSpec matchers simplify testing uploaded image versions and dimensions with have_dimensions, be_no_wider_than, and be_no_larger_than.

ParallelTests::Cucumber::FailuresLogger now emits valid rerun arguments in version 4.9.1, so patched custom loggers can be removed and the default logger restored.

Browser scrolling can switch between instant and animated movement depending on CSS, JavaScript options, and user settings; behavior and scroll-behavior interact in surprising ways.

AppArmor can block daemons after configuration changes, causing misleading file-access errors such as "File not found" or "Can't open file or directory".

rake middleware reveals the ordered Rails request stack, useful for adding, removing, or profiling middleware that runs on every request.

PostgreSQL character columns differ mainly in declared limits, not speed; unbounded varchar and text behave alike in Rails 4+, though some tools still render them differently.

Unpoly popups outside a surrounding form can drop filter values on submit; mirroring inputs between a root form and overlay form preserves pagination and search state.

Ruby 3.0 stops auto-converting hashes to keyword arguments, breaking some method calls and delegation code across Ruby versions.

Animated GIF uploads can slow Rails workers and waste processing time; dropping all but the first frame with ImageMagick avoids resizing work.

JavaScript has no built-in deep equality check for objects and arrays; use _.isEqual(), up.util.isEqual(), or isDeepStrictEqual() for value comparison.