Polyglot persistence uses different databases for different needs:
Example architecture:
- PostgreSQL: User accounts, transactions (ACID)
- MongoDB: Product catalog (flexible schema)
- Redis: Sessions, caching (speed)
- Elasticsearch: Search (full-text)
- Cassandra: Event logs (write scale)
Benefits:
- Each database optimized for its use case
- No single database bottleneck
Challenges:
- Operational complexity (multiple systems)
- Data consistency across systems
- Team expertise requirements
Start simple. Add specialized databases when you hit clear limitations.