Rails APM Quickstart: Scout vs Sentry in 2025

TL;DR

If you just want the gist without all the scroll:

Scout APM

• Rails (and Python) apps are our wheelhouse. We’ve been tuning for them for years.
  
• Includes APM, error monitoring (beta), and logs in one dashboard.
  
• Fast install, zero weird config rabbit holes.
  
• Built for lean teams that need answers, not dashboards to babysit.
  
  

Sentry APM

• Rich, multi-faceted error tracking across tons of languages.
  
• Rails APM is newer and less deep on framework quirks.
  
• More knobs to tweak, especially if you want to keep your event bill from exploding.
  
  

It’s 3 am, do you know what your apps are doing?

It’s (very late) Friday night. You’re sleeping peacefully after a long work week when your phone goes off.

• Background jobs are crawling. Errors are trickling out inconsistently.
  
• The VPN isn’t working; no logs yet –  try to fix it, try to wake up.
  
• You think you’ve found the problem… but now you’re juggling your APM tab, your error tracker, and struggling to get logs on your laptop screen because you don’t want to trek down the stairs to your desk with the big monitors.
  
  

With Scout, you just… don’t. You see the slow trace, the actual error, and the relevant logs all in one place. Fewer tabs. Faster fixes. More sleep.

Install Speed: How Long Until You See Data?

Time-to-first-insight matters.

Scout for Rails — about as fast as installing a gem gets:

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2# Gemfile
3gem "scout_apm"

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2bundle install
3export SCOUT_KEY=your-key-here
4export SCOUT_ERRORS_ENABLED=true
5rails server

When your app restarts, you’ve got metrics, traces and errors (beta) in the dashboard. Want logs? You’re one more gem and config setting (or environment variable) away. 

Sentry APM for Rails — not bad if you’re already set up for errors, but a bit more setup:

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# Gemfile
gem "sentry-rails"

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# config/initializers/sentry.rb
Sentry.init do |config|
  config.dsn = ENV["SENTRY_DSN"]
  config.traces_sample_rate = 0.5
end

Then you’ll probably spend a little time tuning what spans you actually care about so you don’t blow through your quota on background noise ‘cause Rails has a lot to say. 

Let’s Get Down to the Nitty Gritty: Where Each One Wins

If you live in Rails land and want all your “something’s amiss” data in one place, Scout is a better native fit.

If you’re already deep in Sentry for errors, and APM is just a “nice to have,” adding their tracing might be all you need. Just keep in mind that it’s not as Rails-savvy.

Quickstart: Scout APM for Rails (Errors + Logs Included)

1. Add the gem to your Gemfile
   

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gem "scout_apm"
gem “scout_apm_logging”

2. Get your key from your Scout account.
   
3. Set the environment variables
   

export SCOUT_KEY=your-key
export SCOUT_ERRORS_ENABLED=true
export SCOUT_LOGS_MONITOR=true
export SCOUT_LOGS_INGEST_KEY=aaaa-1111-aaaa-1111 # Provided in App Logs Page

4. Restart your app and see:
   
   • Top endpoints by response time
     
   • Detailed SQL breakdowns
     
   • N+1 query alerts
     
   • Background job timings
     
   • Error events (beta)
     
   • Logs tied directly to traces
     
     

When I’d Pick Scout Over Sentry

• My stack is mostly Rails or Django/Flask/FastAPI.
  
• I want APM, errors, and logs without relying on multiple tools and vendors.
  
• I need pricing that doesn’t make me sweat runaway error spikes with every deploy.
  
• I am sleep-deprived and really need to get back to bed as quickly as possible.
  
  

When I’d Pick Sentry Over Scout

• My team uses a bunch of languages/frameworks.
  
• I’m already paying for and am happy with their error tracking.
  
• I just want “good enough” APM without adding another tool or vendor.
  
  

Further Reading

• Here's What Software Errors Could be Costing your Business
  
• Error Monitoring - The Necessary Application Feature
  
• Understanding Heroku Error Codes with Scout
  

FAQ

Will Scout slow down my app?
No — overhead is usually 1–2% in Rails apps.

Can I run both tools?
Yep. Just filter duplicate error reporting so you’re not drowning in noise.

Does Scout work in staging?
Yes — set SCOUT_MONITOR=true in your staging environment.

Can Scout optimize my sleep schedule?
No, but we recommend no screens for an hour before bedtime, and some binaural beats in the delta (1 to 4 Hz) range