Synchronous Inter-Service Communication in Microservices
What is Synchronous Communication?
Caller waits for response.
Service A
↓
Request
↓
Service B
↓
Response
↓
Service A continues
Characteristics:
- ✅ immediate response
- ✅ request-response model
- ✅ easier to understand
- ❌ tight coupling
- ❌ latency propagation
- ❌ cascading failures
Spring Boot HTTP Communication Options
Option 1 — RestTemplate
restTemplate.getForObject(...)
Status:
- Legacy
- Maintenance Mode
Still found in many enterprise systems.
Option 2 — WebClient
webClient.get()
Status:
- Current Spring Recommendation
Advantages:
- non-blocking
- reactive
- modern
Option 3 — OpenFeign
@FeignClient("customer-service")
Status:
- Most Popular in Spring Cloud Microservices
Advantages:
- declarative
- clean code
- integrates with service discovery
Typical Enterprise Evolution
Many organizations moved like this:
RestTemplate
↓
Feign
↓
Feign + WebClient
| Technology | Modern Usage | Banking Usage |
|---|---|---|
| RestTemplate | Legacy | Existing systems |
| WebClient | High | New services |
| OpenFeign | Very High | Most common |
| gRPC | Growing | High-performance services |
| SOAP | Legacy | Core banking integration |
| GraphQL | Limited | API aggregation |
| Direct DB Access | Avoid | Anti-pattern |
| Service Mesh | Advanced | Large platforms |