Ruby at Scale

Real-world concurrency and performance problems you'll face running Ruby in production with hands-on challenges and solutions.

Who is this for?

Ruby developers who want to go beyond CRUD and learn how to handle high traffic, concurrency, and distributed systems, the stuff that breaks at scale.

Problems

Problem	Description	Difficulty
Cache Stampede	Prevent 1000 concurrent requests from hammering your DB when cache expires	Medium
Rate Limiter	Atomic sliding window rate limiting under high concurrency	Medium

How it works

1. Read the challenge file
2. Implement your solution
3. Run the test to verify
4. Compare with the provided solution

Setup

bundle install

Update config/database.yml with your PostgreSQL credentials, then:

rake db:create
rake db:migrate

Run

bin/server

Test

# Unit/Integration specs
rspec --tag ~system

# System tests (interactive, requires running PostgreSQL and Redis)
spec/system/bin/cache_stampede_test
spec/system/bin/rate_limiter_test

Dependencies

Dependency	Purpose
PostgreSQL	Simulates expensive database queries
Redis	Cache store and distributed lock backend
Ruby	4.0+

⚠️ Note

Tests delete specific Redis keys before running. They do not call flushdb - your other Redis data is safe but make sure you don't run it on critical infra.

Blog

For a full technical deep-dive on the cache stampede problem, solutions, and tradeoffs: Thundering Herd: The Problem That Kills Ruby Apps at Scale