15 Years of Rails With Domain Driven Design - Lessons Learnt
summary
Fast, practical account of converting a 10‑year Rails app into 50 modules (16 read models, 20 process managers, 14 domains) where most modules are under 500 LOC and a typical read model is ~80 LOC. Shows an explicit algorithm: create domains/read_models/process_managers directories, install rails_event_store, pick one slow view, design a read model schema, map events to columns, publish events alongside existing code and compare until identical. Covers agent work with Claude, where agents speed coding but hit business‑logic and performance limits, and recommends mutation testing with mutant and the Rails Event Store gem.
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chapters (10)
- 0:00Introduction
- 4:26Rails architecture challenges
- 8:41DDD as Rails solution
- 11:11Modular Rails with DDD
- 12:37Read models for performance
- 16:52Domains and process managers
- 20:46Data flow in DDD Rails
- 23:14Adopting DDD in legacy Rails
- 27:29Removing callbacks
- 28:11Mutation testing
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