Modeling software around business
Day 112 of 149
👉 Full deep-dive with code examples
The Hospital Analogy
A hospital has distinct departments:
- Emergency → Speaks in urgency and triage
- Pharmacy → Speaks in medications and dosages
- Billing → Speaks in codes and insurance
Each department has its own vocabulary and rules. You don't apply emergency room logic to billing!
Domain-Driven Design organizes software around these real business departments!
The Problem It Solves
In complex businesses:
- Developers use technical terms
- Business people use domain terms
- Miscommunication leads to wrong software
"We need a customer entity" vs "We need to track patient admissions"
Core Ideas
Ubiquitous Language:
- Everyone uses the same terms
- "Patient" not "user" in healthcare
- "Order" not "purchase" in e-commerce
- No translation needed between teams
Bounded Contexts:
- Different parts of the system have different meanings
- "Product" in inventory ≠ "Product" in shipping
- Each context owns its own definitions
Example: E-Commerce
Different contexts, different "Order" meanings:
- Sales: Order = customer's purchase intent
- Fulfillment: Order = items to pick and pack
- Billing: Order = invoice to generate
Same word, different context, different behavior!
Benefits
- Less miscommunication → Speak business language in code
- Clearer boundaries → Each context is independent
- Easier evolution → Change one context without breaking others
- Better collaboration → Developers and business united
When To Use DDD
Good for:
- Complex business domains
- Large teams
- Long-term projects
Overkill for:
- Simple CRUD apps
- Small projects
- Technical utilities
In One Sentence
Domain-Driven Design structures software around real business concepts and language, so code reflects how the business actually works.
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