| Monolithic codebase |
Fast to build, easy to deploy |
Transaction volume grows and teams need to scale individual services independently |
Migrate to modular or microservices architecture |
| Single relational database |
Simple to manage, ACID-compliant |
Concurrent transaction load exceeds single-node capacity |
Database sharding, read replicas, or distributed SQL |
| Synchronous API calls |
Easy to reason about and debug |
Downstream services slow down or fail under load |
Event-driven architecture with async message queues |
| On-premise infrastructure |
Low initial cost, predictable environment |
Traffic spikes require capacity that cannot be provisioned quickly |
Cloud-native infrastructure with auto-scaling |