Performance

Application Performance Monitoring

• NewRelic
• Skylight.io
• Scout
• rack-mini-profiler
• rails-mini-profiler
• Splunk

Linting

• rubocop-performance

Database query performance

• Bullet gem
• PgHero

Ruby Profiling

• https://ruby-prof.github.io/
• RbSpy
• RubyMine (uses RbSpy to profile tests)
• Vernier Profiler

Memory profiling

• SamSaffron/memory_profiler

Related reading

• Google SRE Book
• DataDog Learning Center
• Benchmarking vs Profiling
• The Complete Guide to Rails Performance by Nate Berkopec