1. 1. Intro
2. 2. Ractors, what and why
3. 3. Ruby heap
4. 4. Counter, the wrong way
5. 5. Atomics
6. 6. Counter, the right way
7. 7. Containers, Ractors, and GC
8. 8. Concurrent HashMap
9. 9. Concurrent ObjectPool
10. 10. (Naive) Concurrent Queue
11. 11. Parallel Test Framework
12. 12. A Better Queue
13. 1. 12.1. Lock Free MPMC Queue
    2. 12.2. Adding Blocking Interface
    3. 12.3. Marking
    4. 12.4. Writing a Web Server
14. 13. Conclusion