Microservices vs Monolith: Making the Right Architecture Decision

Amazon, Netflix, and Uber use microservices — but Shopify ($100B+ company) runs on a modular monolith. The right choice depends on your team, scale, and complexity.

Monolith Advantages

✓ Simple deployment — one artifact
✓ Easy debugging — single process
✓ No network latency between components
✓ Simple transactions with database ACID
✓ Lower operational overhead
✓ Faster for teams under 10 developers

Microservices Advantages

✓ Independent deployment per service
✓ Technology diversity per service
✓ Team autonomy — each team owns their service
✓ Fault isolation
✓ Independent scaling
✓ Organizational scaling for 50+ developers

The Modular Monolith (Best of Both)

app/Modules/
├── Users/
│   ├── Controllers/
│   ├── Models/
│   ├── Services/
│   └── Events/
├── Orders/
│   ├── Controllers/
│   └── ...
└── Payments/

Rules:
1. Modules communicate via events, not direct imports
2. Each module owns its database tables
3. No cross-module Eloquent relationships
4. Shared kernel only for truly shared code

Decision Framework

Start with monolith if:
  → Team < 10 developers
  → Product in early stage
  → Simple domain

Consider microservices if:
  → Team > 30 developers across squads
  → Different components need independent scaling
  → Organization has DevOps maturity (CI/CD, K8s)

Migration Path

Monolith → Modular Monolith → Microservices

1. Identify bounded contexts
2. Extract into modules with clear interfaces
3. Replace direct calls with events
4. Extract high-traffic modules into services
5. Add API gateway and service discovery

Start with a monolith, structure it well, and only extract services when you have a clear need and operational maturity.