Database Read Replica Query Router

Implement read replica query routing for this setup:

**Database System:** {{DATABASE_SYSTEM}}
**Application Stack:** {{APPLICATION_STACK}}
**Replica Configuration:** {{REPLICA_CONFIG}}
**Read/Write Patterns:** {{RW_PATTERNS}}
**Consistency Requirements:** {{CONSISTENCY}}

Please provide:
1. Routing strategy design
2. Implementation approaches:
   - Application-level routing
   - Proxy-based routing
   - Driver-level routing
3. Read-after-write consistency handling
4. Failover logic
5. Load balancing between replicas
6. Health checking replicas
7. Code examples for routing
8. Session affinity handling
9. Monitoring replica lag
10. Testing routing logic