Strangler Fig Pattern

Incrementally extract services from a monolith while routing selected traffic to the new system.

migration

Detailed Description

Instead of rewriting everything, the new system grows around the old one. Features are moved one at a time.

This is usually safer than a big-bang migration because production traffic validates each extracted service gradually.

Visual Diagram

Monolith → Microservices migration
Step 1: Monolith handles everything
Step 2: Extract UserService, route user traffic
         Monolith → UserService
Step 3: Extract OrderService next
Step N: Monolith retires completely

Tradeoffs

Pros

Incremental, safer migration, lower rewrite risk

Cons

Temporary dual maintenance and routing complexity

Examples: Real-world monolith to microservice migrations